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MARYLAND 


GEOLOGICAL  SURVEY 


CAMBRIAN  AND  ORDOVICIAN 


BALTIMORE 

THE  JOHNS  HOPKINS  PRESS 
IQIQ 


'XCH 


JSorft  (gaftttnore  (preee 

BALTIMORE,  MD.,  U.  8.  A. 


SCIENCES 


COMMISSION 


EMERSON  C.  HARRINGTON,  .        .     .   .        .        PBESIDENT. 

GOVERNOR  OF  MARYLAND. 

HUGH  A.  McMULLEN,      .        .        .        .        .        .        .        .        i 

COMPTROLLER  OF  MARYLAND. 

FRANK  J.  GOODNOW,        .        .  .        EXECUTIVE  OFFICEE. 

PRESIDENT  OF  THE  JOHNS   HOPKINS  UNIVERSITY. 

A.  F.  WOODS, .        .        SECEETAEY. 

PRESIDENT  OF  THE  STATE  COLLEGE  OF  AGRICULTURE. 


416455 


SCIENTIFIC  STAFF 


EDWARD  BENNETT  MATHEWS,      ....        STATE  GEOLOGIST. 
SUPERINTENDENT  OF  THE  SURVEY 


EDWARD  W.  BERRY,  .        .        .        ASSISTANT  STATE  GEOLOGIST. 

CHARLES  K.  SWARTZ, GEOLOGIST. 

J.  T.  SINGEWALD,  JR.,          ' GEOLOGIST. 

EUGENE  H.  SAPP,          .        .        .        ....        .        ASSISTANT. 

Miss  MYRA  ALE, SECRETARY. 


LETTER  OF  TRANSMITTAL 

To  His  Excellency  EMEKSON  C.  HARRINGTON, 

Governor  of  Maryland  and  President  of  the  Geological  Survey  Com- 
mission, 

Sir: — I  have  the  honor  to  present  herewith  the  seventh  of  a  series  of 
reports  dealing  with  the  systematic  geology  and  paleontology  of  Maryland. 
The  preceding  reports  of  this  series  have  dealt  with  the  Devonian,  Lower 
Cretaceous,  Upper  Cretaceous,  Eocene,  Miocene,  and  Plio-Pleistocene 
deposits  and  the  remains  of  animal  and  plant  life  which  they  contain. 
The  present  volume  treats  of  the  Cambrian  and  Ordovician  deposits  and 
their  contained  life.  These  rocks  comprise  the  oldest  fossiliferous  rocks 
of  the  state,  a  knowledge  of  which  is  extremely  important  from  a  scientific, 
educational,  and  economic  standpoint.  I  am, 

Very  respectfully, 

EDWARD  BENNETT  MATHEWS, 

State  Geologist. 
JOHNS  HOPKINS  UNIVERSITY, 

BALTIMORE,  September,  1919. 


PAGB 

PREFACE   19 

THE  CAMBRIAN  AND  ORDOVICIAN  DEPOSITS  OP  MARYLAND.    BY 

R.  S.  BASSLEB 21 

INTRODUCTION    23 

THE  PHYSIOGRAPHY 23 

THE  GEOLOGY 24 

HISTORICAL  REVIEW  25 

BIBLIOGRAPHY   34 

PALEOGEOGRAPHY  OF  THE  CAMBRIAN  AND  ORDOVICIAN 45 

STRATIGRAPHIC  AND  PALEONTOLOGIC  CHARACTERISTICS 50 

CAMBRIAN  SILICEOUS  FORMATIONS 52 

The  London  Formation 53 

The  Weverton  Sandstone 54 

The  Harpers  Shale 57 

The  Antietam  Sandstone 58 

CAMBRIAN-ORDOVICIAN    LIMESTONES 60 

The  Tomstown  Limestone 61 

Topography 61 

Lithologic  Characters 62 

Residual  Products 63 

Economic  Features 64 

Areal  Distribution 65 

Thickness  66 

Age  and  Correlation 66 

The  Waynesboro  Formation 66 

Name  and  Synonymy 67 

Lithologic  Character  and  Thickness 68 

Topographic  Form 69 

Tomstown — Waynesboro  Boundary 69 

Areal  Distribution 70 

Economic  Features V 1 

Age  and  Correlation 71 

The  ElbrooTc  Formation 72 

Lithologic  Character  and  Thickness 72 

Areal  Distribution 72 

Topographic  Form  and  Residual  Products 73 

Age  and  Correlation 74 

The  Conococheague  Limestone 74 

Lithologic  Character  and  Thickness 76 

Topography • 81 

Areal  Distribution 81 

Age  and  Correlation 82 

Cryptozoon  Reefs 83 

Edgewise  Conglomerate  86 


CONTENTS 

PAGE 

Fossils  of  Cambrian  Age 88 

The  Beekmantown  Limestone 89 

Lithologic  Character 92 

Faunal  Zones 96 

Stonehenge  Member 96 

Cryptozoon  steeli  Zone  101 

Ceratopea  Zone   103 

Turritoma  Zone 104 

Topography  and  Residual  Products 105 

Areal  Distribution 109 

Frederick  Valley  Limestones Ill 

The  Beekmantown  Limestone 114 

The  Frederick  Limestone 115 

The  Stones  River  Limestone 117 

General  Sections  117 

Lithologic  Character 121 

Paleontology 121 

Lower  Stones  River 122 

Middle  Stones  River 124 

Upper  Stones  River 126 

Areal  Distribution  and  Topographic  Features 126 

Fauna  of  the  Stones  River  in  Maryland 127 

The  Chambersburg  Limestone 129 

Lithologic  Character   130 

Areal  Distribution 132 

Faunal  Zones  132 

Caryocystites  Bed  133 

Tetradium  cellulosum  Bed 136 

Echinospherites  Bed 139 

Nidulites  Bed  140 

Christiania  Bed  142 

Greencastle  Bed 143 

Sections  of  the  Chambersburg  Limestone 144 

East  of  Martinsburg  Shale  Belt 144 

West  of  Martinsburg  Shale  Belt 147 

Variations  in  Distribution 152 

Age  and  Correlation 153 

UPPER   OEDOVICIAN    SHALES 134 

The  Martinsburg  Shale  154 

Lithologic  Character  and  Sections 157 

Topographic  Features  and  Areal  Distribution 161 

Faunas   163 

Sinuites  Bed  of  Trenton  Age 163 

Corynoides  Bed  of  Trenton  Age 165 

Eden  Division   167 

Maysville  Sandstone  Division 168 

The  Juniata  Formation 170 

TABLES   SHOWING  DISTRIBUTION  OF   SPECIES 174 


CONTENTS  13 

PAGE 

SYSTEMATIC  PALEONTOLOGY,  CAMBRIAN  AND  ORDOVICIAN 187 

THALLOPHYTA,  R.  S.  BASSLER 189 

PoRiFERA,  R.  S.  BASSLER 195 

COELENTERATA,  R.   S.  BASSLER 198 

ECHINODERMATA,  R.   S.  BASSLER 207 

MOLLTJSCOIDEA,  R.   S.   BASSLER 212 

VERMES,  R.  S.  BASSLER 276 

MOLLUSCA,  R.  S.  BASSLER 277 

ARTHROPODA,  R.  S.  BASSLER 332 

GENERAL  INDEX 409 

PALEONTOLOGICAL  INDEX   .417 


ILLUSTRATIONS 


PLATE  FACING  PAQB 

I.     Map  showing  the  Distribution  of  the  Cambrian  and  Ordovician 

Deposits  of  Maryland , .     23 

II.     View  of  the  Potomac  Water  Gap  at  Harper's  Ferry 52 

III.  Fig.  1. — View  of  the  Great  Valley  from  South  Mountain  at  Blue 

Mountain  Station   56 

Fig.  2. — View  along  road  between  Pen  Mar  and  High  Rock,  Mary- 
land, showing  mountain  side  covered  with  blocks  of  Weverton 
quartzite 56 

IV.  Fig.  1. — Exposure  of  Tomstown  limestone  along  trolley  line  just 

southeast  of  Wagner's  Cross  Road,  Washington  County,  Mary- 
land, illustrating  weathering  of  massive  sheared  limestone 
into  shale  fragments 62 

Fig.  2. — Limestone  quarry  at  Cavetown,  Maryland,  showing  Toms- 
town  limestone  faulted  against  Waynesboro  sandstone 62 

V.  Fig.  1. — Valley  of  Tomstown  limestone  looking  east  from  Cave- 
town,  Maryland,  showing  foothills  of  Harpers  shale,  and 
South  Mountain  of  Weverton  sandstone  in  the  distance 64 

Fig.  2. — Valley  of  Tomstown  limestone  with  South  Mountain  in 
the  distance  showing  peneplained  surface.  The  hill  just 
beyond  the  house  is  capped  by  Tomstown  chert.  Photograph 

taken  one  mile  south  of  Cavetown,  Maryland 64 

VI.  Fig.  1. — Overturned  fold  with  slight  faulting  in  Tomstown  lime- 
stone along  Western  Maryland  Railway,  one  mile  west  of 
Cavetown,  Maryland 66 

Fig.  2. — Ridge  of  the  Waynesboro  formation  just  east  of  Middle 

Bridge,  Antietam  Battlefield,  Washington  County,  Maryland . .     66 
VII.    Iron  stained  contorted  sandstone  of  Waynesboro  formation.    The 
upper  figure  represents  the  usual  aspect  of  the  rock.    The 
cavities  in  the  sandstone  are  covered  by  drusy  quartz  as 
shown  in  the  figure  to  the  left  (x2)  or  by  beautiful  minute 

crystals  of  quartz  illustrated  in  figure  to  right  (x  6) 68 

VIII.  Fig.  1. — Exposure  of  Elbrook  limestone  along  Baltimore  and  Ohio 
Railroad  just  south  of  Sharman,  Maryland.  These  massive 
beds  weather  into  thin  shaly  layers 72 

Fig.  2. — View  looking  north  over  Antietam  Battlefield  showing 
exposure  of  Elbrook  limestone.  Photograph  taken  one-half 
mile  east  of  Sharpsburg,  along  road  to  Burnside  Bridge, 
Maryland 72 


16 


ILLUSTRATIONS 


PLATE  FACING  PAGE 

IX.  Fig.  1. — Cryptozoon  reef  at  base  of  Conococheague  formation,  ex- 
posed along  Norfolk  and  Western  Railroad  about  one  mile 
southwest  of  Antietam  Station,  Maryland.  Photograph  about 
one-fifteenth  natural  size 76 

Fig.  2. — Cryptozoon  structure  in  upper  part  of  Conococheague 
limestone  exposed  along  Western  Maryland  Railway,  one- 
quarter  mile  west  of  Charlton,  Maryland.  Photograph  one- 
sixth  natural  size 76 

X.  Fig.  1. — Exposure  of  Conococheague  limestone  on  edge,  along  road 
near  Bakersville,  Maryland.  The  characteristic  strongly 
crinkled,  sandy  laminae  are  well  developed 80 

Fig.  2. — Lower  Conococheague  scoriaceous  chert  exposed  in  fence 
along  Hagerstown  turnpike  just  north  of  Sharpsburg,  Mary- 
land   80 

XI.     "  Edgewise  beds "  characteristic  of  Beekmantown  and  Conoco- 
cheague formations,  Hagerstown  Valley,  Washington  County.     82 
XII.     Fig.  1. — Quarry  in  upper  part  of  Conococheague  limestone  with 

Security  Cement  Works,  Security,  Maryland,  in  distance. ...     84 

Fig.  2. — Typical  exposure  of  the  lower  pure  finely  conglomeratic 
beds  of  the  Stonehenge  limestone  along  National  Highway, 
just  south  of  Funkstown,  Maryland 84 

XIII.  Fig.  1. — Exposure    of    steeply    inclined    Stonehenge    limestone 

(upper  division)    at  Charlton,  Maryland,   showing  the   dis- 
integration into  siliceous  shale,  upon  prolonged  weathering. . .     96 
Fig.  2. — Typical   exposure  of  edgewise   conglomerate   from   the 
upper  part  of  the  Stonehenge  limestone,  Baltimore  and  Ohio 
Railroad,  one  mile  north  of  Balls,  Maryland 96 

XIV.  Fig.  1. — View  of  a  weathered  outcrop  of  the  upper  Stonehenge 

limestone,  eastern  edge  of  Hagerstown,  Maryland 100 

Fig.  2. — View  taken  from  hill  of  upper  Stonehenge  limestone, 
eastern  edge  of  Hagerstown,  Maryland,  looking  east,  showing 
effect  of  weathering  of  the  various  formations  upon  topog- 
raphy   100 

XV.  Fig.  1. — Exposure  of  lower  Beekmantown  limestone  just  above 
the  Stonehenge  member  in  brickyard,  eastern  edge  of  Hagers- 
town, Maryland.  Clay  for  brick  manufacture  results  from  the 

weathering  of  the  purer  beds 104 

Fig.  2. — Beekmantown  limestone  at  LeGore  quarry,  LeGore,  Mary- 
land. The  weathered  outcrops  of  these  strata  have  yielded 

numerous  cephalopods 104 

XVI.     Fig.  1. — Near  view  of  Beekmantown  limestone  at  LeGore  quarry, 
LeGore,  Maryland.     Strata  penetrated  by  a  six-inch  diabase 

dyke  (marked  by  hammer) 108 

Fig.  2. — View  of  contact  between  the  Beekmantown  (B)  and 
Stones  River  (S)  limestone  along  the  south  side  of  the 
National  Highway  at  Wilson,  Maryland.  The  zone  of  cauli- 
flower chert  (C)  is  well  displayed  at  this  place 108 


ILLUSTRATIONS  17 

PLATE  FACING  PAGE 

XVII.  Fig.  1. — An  average  example  of  the  cauliflower  chert  from  the 
base  of  the  Stones  River  limestone.  Vicinity  of  Bostetter, 
Maryland 120 

Fig.  2. — Typical  natural  outcrop  of  upper  Stones  River  limestone 
in  cleared  fields,  one-half  mile  west  of  Pinesburg,  Maryland. 
The  growth  of  cedar  trees  on  this  pure  limestone  is  illustrated.  120 
XVIII.  Fig.  1. — View  of  edgewise  conglomerate  in  Stones  River  forma- 
tion, two  and  one-half  miles  southeast  of  Williamsport,  Mary- 
land    122 

Fig.  1. — View  of  quarry  in  Chambersburg  limestone  at  Pinesburg 

Station,  Maryland 122 

XIX.  Fig.  1. — Photograph  showing  succession  of  sinks  along  the  band 
of  outcrop  of  the  Stones  River  limestone,  one-half  mile  south 
of  Wilson,  Maryland.  The  road  to  the  east  follows  the  Cham- 
bersburg limestone 126 

Fig.  2. — Near  view  of  a  sink  filled  with  water 126 

XX.  Fig.  1. — Typical  exposure  of  the  Echinospherites  bed  of  the  Cham- 
bersburg limestone  showing  characteristic  cobbly  effect.  Rail- 
road cut  at  Pinesburg  Station,  Maryland 130 

Fig.  2. — Typical  outcrop  of  steeply  dipping  Chambersburg  lime- 
stone along  road  between  Pinesburg  and  Pinesburg  Station, 

Maryland 130 

XXI.  Fig.  1. — View  in  the  Tabler  quarry  just  south  of  Frederick,  Mary- 
land, showing  contact  of  the  massive  Beekmantown  limestone 
overlaid  by  the  thin-bedded  Frederick  limestone  with  a  dis- 
tinct line  of  unconformity  separating  them 160 

Fig.  2. — Fold  in  sandy  upper  (Eden)  portion  of  Martinsburg 
shale  along  Western  Maryland  Railway,  three-fourths  mile 

west  of  Williamsport,  Maryland 160 

XXII.  Fig.  1. — Exposure  of  lower  part  of  Martinsburg  shale  along 
Western  Maryland  Railway,  about  one-half  mile  east  of  Pines- 
burg Station,  Maryland.  The  gentle  dip  of  the  strata  and  the 
cleavage  at  right  angles  are  well  shown 104 

Fig.  2. — View  across  valley  of  Conococheague  and  Beekmantown 
limestones,  from  a  point  two  miles  east  of  Little  Georgetown, 
West  Virginia.  Conococheague  chert  strews  the  foreground. 
North  Mountain  in  the  distance  contains  the  Juniata  and 

Tuscarora  formations 164 

XXIII.  Fig.  1. — View  of  Martinsburg  shale  topography,  looking  northeast 
from  a  point  one-half  mile  south  of  Wilson,  Maryland.  Cono- 
cocheague Creek  is  seen  in  the  foreground  and  the  National 
Highway  in  the  middle 170 

Fig.  2.— Valley  of  Martinsburg  shale  (Blair  Valley,  Maryland) 
viewed  from  road,  just  west  of  Union  Bethel  Church.  The 
mountains  on  both  sides  are  formed  of  the  Juniata  and  Tus- 
carora formations 170 

XXIV  to  LVI1I.     Systematic  Paleontology 374-408 


18  ILLUSTRATIONS 

FIGURE  PAGE 

1.  Columnar  section  of  the  Cambrian,  Ozarkian,  and  Canadian  strata  of 

Maryland  48 

2.  Columnar  section  of  the  Ordovician  rocks  of  Maryland 49 

3.  Cambrian-Ordovician  Correlation  Table 51 

4.  Paleogeographic  map  of  Lower  Cambrian  (Waucoban) 55 

5.  Paleogeographic  map  of  Middle  Cambrian  (Acadian) 55 

6.  Paleogeographic  map  of  Upper  Cambrian  (St.  Croixan) 75 

7.  Paleogeographic  map  of  Early  Ozarkian  (Conococheague) 75 

8.  Paleogeographic  map  of  Upper  Ozarkian  (Copper  Ridge) 79 

9.  Paleogeographic  map  of  Late  Ozarkian  (Chepultepec) 79 

10.  Paleogeographic  map  of  Lower  Canadian  (Bretonian) 91 

11.  Paleogeographic  map  of  Middle  and  Late  Canadian  (Beekmantown) .  91 

12.  Structure  Sections  across  Frederick  Valley 112 

13.  Paleogeographic  map  of  Early  Ordovician  (St.  Peter) 119 

14.  Paleogeographic  maps  of  Early  Ordovician  (Mosheim) 119 

15.  Paleogeographic  map  of  Early  Ordovician   (Middle  Stones  River) 

Maclurites  magnus  fauna 125 

16.  Paleogeographic  map  of  Early  Ordovician  (Upper  Stones  River) 125 

17.  Diagrammatic  section  of  Chambersburg  limestone  from  Chambers- 

burg,  Pa.,  to  Strasburg,  W.  Va 131 

18.  Paleogeographic  map  of  Early  Ordovician  (Blount) 134 

19.  Paleogeographic  map  of  Middle  Ordovician.     Lower  Black  River 

(Lowville)  134 

20.  Paleogeographic  map  of  Middle  Ordovician.     Middle  Black  River 

(Decorah)    138 

21.  Paleogeographic  map   of  Middle  Ordovician.     Upper  Black  River 

(Kimmswick)     138 

22.  Paleogeographic  map  of  Middle  Ordovician.    (Latest  Chambersburg) .  155 

23.  Paleogeographic  map  of  Middle  Ordovician  (Early  Trenton) 155 

24.  Paleogeographic    map    of    Late    Ordovician.      Early    Cincinnatian 

(Utica)  159 

25.  Paleogeographic  map  of  Late  Ordovician.    Cincinnatian  (Eden) 159 

26.  Paleogeographic  map  of  Late  Ordovician.    Cincinnatian  (Fairview) .  162 

27.  Paleogeographic  map  of  Late  Ordovician.    Cincinnatian  (Oswego  or 

McMillan)    162 


PREFACE 

The  present  volume  is  the  seventh  of  a  series  of  reports  dealing  with 
the  systematic  geology  and  paleontology  of  Maryland,  the  Devonian, 
Lower  Cretaceous,  Upper  Cretaceous,  Eocene,  Miocene  and  Plio-Pleisto- 
cene  deposits  having  already  been  fully  described. 

This  volume  is  devoted  to  a  consideration  of  .the  Cambrian  and  Ordo- 
vician  deposits  and  their  contained  faunas.  The  calcareous  strata  making 
up  a  considerable  part  of  these  two  systems  are  so  intimately  united  in  the 
Appalachians  that  they  have  long  remained  unseparated  under  the  name 
Cambro-Ordovician  limestone,  or,  as  in  Maryland  and  Virginia,  the 
Shenandoah  limestone.  It  was  therefore  thought  eminently  fitting  to 
combine  their  consideration  in  one  volume  and  to  disregard  in  the  title 
the  Ozarkian,  the  Canadian,  and  other  possible  systems  which  have  been 
suggested  in  recent  years. 

Upon  the  completion  of  studies  on  the  Cambrian  and  Ordovician  rocks 
of  Virginia  in  1909,  published  as  Bulletin  2 A  of  the  Virginia  Geological 
Survey  under  the  title  "  Cement  Resources  of  Virginia  west  of  the  Blue 
Ridge,"  the  writer,  upon  the  invitation  of  the  late  Dr.  William  Bullock 
Clark,  undertook  the  preparation  of  the  Maryland  volume  dealing  with 
the  systematic  geology  and  paleontology  of  the  Cambrian  and  Ordovician 
systems.  As  this  work  included  the  mapping  of  these  strata  in  areas  both 
west  and  east  of  the  Blue  Ridge,  and  as  only  a  few  weeks  were  available 
each  summer  for  the  necessary  field  work,  the  volume  has  been  long 
delayed.  However,  this  delay  has  proved  fortunate,  for  during  the 
interval  of  its  preparation  the  knowledge  of  Cambrian  and  Ordovician 
stratigraphy  has  progressed  so  much  that  it  is  hoped  fewer  mistakes 
will  now  be  recorded. 

During  the  preparation  of  the  Mercersburg-Chambersburg  folio  descrip- 
tive of  the  region  in  Pennsylvania,  just  north  of  the  Maryland  state  line, 


20  PREFACE 

the  writer  had  the  advantage  of  association  with  E.  0.  Ulrich  and  George 
W.  Stose  in  their  studies  of  the  stratigraphy  and  paleontology  of  that 
area.  He  thus  helped  to  collect  the  data  and  became  acquainted  with  the 
Cambrian  and  Ordovician  faunas  and  sections  which  are  so  well  displayed 
there,  but  not  as  well  developed  in  Maryland. 

Dr.  Richard  C.  Williams,  while  a  graduate  student  at  Johns  Hopkins 
University,  assisted  in  the  mapping  of  the  Cambrian  and  Ordovician 
strata,  especially  in  the  Hagerstown  area.  The  Maryland  Geological 
Survey  has  also  had  the  cooperation  of  the  IT.  S.  Geological  Survey, 
Mr.  George  W.  Stose  of  that  organization  being  associated  in  the  field 
work  in  the  Williamsport  quadrangle  in  the  area  west  of  the  Martinsburg 
shale  belt. 

The  Survey  is  also  indebted  to  Dr.  E.  0.  Ulrich  of  the  U.  S.  Geological 
Survey  for  permission  to  incorporate  in  this  volume  a  set  of  his  paleo- 
geographic  maps  covering  the  Cambrian  and  Ordovician  formations. 


THE  CAMBRIAN  AND  ORDOVICIAN 
DEPOSITS  OE  MARYLAND 


MARYLAND  GEOLOGICAL  SURVEY 


MAP 

SHOWING  THE  DISTRIBUTION  OF  THE 

CAMBRIAN  AND  ORDOVICIAN  FORMATIONS 

OF 

MARYLAND 

BY  K.  8.  BAS8LER 


1919 

LEGEND 


Of    !  Frederick  limestone 


Om        Martiuslmrtf  shale 


MARYLAND  GEOLOGICAL  SURVEY 
EDWARD  BENNETT  MATHEWS.  STATE  GEOLOGIST 


SCAI.K  :    One  inch  equals  five  miles 
1:312,500 


Cc 


Conococheague  limestone 


Ce        Klbrook  limestone 


•  Waynesboro  formation 
Ct     I  Tomstown  limestone 


Silurian  and  Devi 
Pre  Cambrian  coi 


„,]   Antietam,  Harpers,  Weverton 
and  Loudon 

WOO 


Beekmantowu  limestone 
Newark  formation 


77°50' 


77°  40' 


CAMBRIAN— ORDOVICIAN      PLATE  I 


77°io' 


77°20' 


THE  CAMBRIAN  AND  ORDOVICIAN 
DEPOSITS  OF  MARYLAND 

BY 
R.  S.  BASSLER 

INTRODUCTION 

The  Cambrian  and  Ordovician  deposits  of  Maryland  can  only  be 
interpreted  through  an  understanding  of  the  geology  of  the  extensive 
province  extending  from  eastern  Canada  to  Alabama,  of  which  the  State 
of  Maryland  forms  a  part.  The  Cambrian  and  Ordovician  formations  of 
Maryland  extend  far  beyond  the  confines  of  the  state  and  in  adjacent  areas 
to  the  north  or  south  frequently  afford  more  satisfactory  evidence  of  their 
character  and  fossil  content  than  they  do  in  Maryland. 

THE  PHYSIOGEAPHY 

The  region  here  considered  forms  a  small  portion  of  the  Atlantic  slope, 
which  stretches  from  the  crest  of  the  Alleghanies  to  the  sea,  and  which  is 
divided  into  three  more  or  less  sharply  defined  physiographic  regions 
known  as  the  Appalachian  Region,  the  Piedmont  Plateau,  and  the  Coastal 
Plain.  These  three  districts  follow  the  Atlantic  border  of  the  United 
States  in  three  belts  of  varying  width  from  New  England  southwestward 
to  the  Gulf  states. 

The  Appalachian  Region  extends  from  beyond  the  western  limits  of  the 
state  eastward  to  the  Blue  Ridge  and  is  divided  into  three  districts  known 
as  the  Alleghany  Plateau,  the  Greater  Appalachian  Valley,  and  the  Blue 
Ridge  District.  The  first  is  west  of  the  Alleghany  Front  and  contains 
rocks  younger  than  Ordovician.  Extending  along  the  eastern  border  of 
the  Alleghany  Front  is  the  district  known  as  the  Greater  Appalachian 
Valley  which  admits  of  a  twofold  division  into  the  zone  of  Alleghany 


24        THE  CAMBRIAN  AND  ORDOVICIAN  DEPOSITS  OF  MARYLAND 

Eidges  on  the  west  and  the  Great  Valley  on  the  east,  the  latter  known  as 
the  Hagerstown  Valley  in  Maryland,  the  Cumberland  Valley  in  Pennsyl- 
vania, and  the  Shenandoah  Valley  in  Virginia.  The  Great  Valley  is  a 
broad  lowland  with  an  elevation  averaging  between  500  and  600  feet  and 
gradually  increasing  in  height  to  the  northward.  It  extends  from  New 
York  state  to  Alabama  and  in  Maryland  lies  between  North  Mountain 
on  the  west  and  the  Blue  Eidge  on  the  east.  The  Blue  Eidge  district  con- 
sists of  the  Blue  Eidge  and  Catoctin  mountains  which  unite  immediately 
north  of  the  Maryland-Pennsylvania  boundary  to  form  the  greater  high- 
land known  as  South  Mountain. 

The  Piedmont  Plateau  borders  the  Blue  Eidge  district  on  the  east  and 
comprises  the  hill  country  of  ancient  rocks  lying  between  the  Blue  Eidge 
on  the  west  and  the  Coastal  Plain  district  on  the  east — the  latter  district 
sloping  gradually  to  the  southeast  and  becoming  submerged  beneath  the 
Atlantic.  The  Piedmont  Plateau  is  divided  into  an  Eastern  Division  and 
a  Western  Division  by  the  upland  known  as  Parr's  Eidge  which  forms  the 
low  divide  at  an  average  elevation  of  between  800  and  900  feet  of  the 
streams  flowing  directly  into  Chesapeake  Bay  and  those  flowing  into 
Potomac  Eiver.  The  Western  Division  in  Maryland  corresponds  rather 
closely  to  what  is  known  as  the  Frederick  Valley. 

THE  GEOLOGY 

The  Cambrian  and  Ordovician  formations  in  Maryland  are  confined 
to  the  eastern  division  of  the  Appalachian  Eegion,  previously  described 
as  the  Great  Valley  and  Blue  Eidge,  and  to  the  western  division  of  the 
Piedmont  Plateau  Eegion. 

The  Cambrian  formations  consist  of  shales,  limestones,  and  sandstones 
of  sedimentary  origin  which  have  been  subjected  to  much  metamorphism 
and  marked  structural  disturbances  since  they  were  deposited.  They 
cover  considerable  areas  in  Washington  and  Frederick  counties.  The 
Ordovician  formations  are  found  in  association  with  the  Cambrian  in  the 
Great  Valley  and  Blue  Eidge  regions  and  also  in  the  Frederick  Valley. 
The  Ordovician  sediments  have  been  much  folded  and  faulted,  but  they 
are,  on  the  whole,  less  metamorphosed  than  those  of  Cambrian  age. 


MARYLAND  GEOLOGICAL  SURVEY  25 

HISTOKICAL  EEVIEW 

It  will  be  remembered  that  previous  to  1830  geologists  grouped  into  a 
single  large  and  indefinite  "  Transition  Series  "  all  of  the  sedimentary 
and  interbedded  volcanic  rocks  of  Great  Britain  older  than  the  Car- 
boniferous. Immediately  underlying  the  Carboniferous  was  the  great 
mass  of  red  sandstones  and  marls  first  designated  the  Old  Eed  sandstone 
and  later  determined  as  of  Devonian  age.  In  1831,  Sir  Eoderick  I. 
Murchison  and  Professor  Adam  Sedgwick  attacked  the  problem  of  the 
division  of  the  remaining  underlying  strata,  confining  their  studies  to 
the  rocks  of  western  England  and  eastern  and  southeastern  Wales. 
Murchison  undertook  this  study  under  favorable  circumstances,  as  he 
began  his  researches  at  the  upper  end  of  the  series  where  fossils  abound 
and  the  structure  is  simple.  He  found  that  the  different  members  of  the 
upper  part  of  this  great  series  could  be  recognized  by  the  fossils  as  easily 
as  more  recent  strata,  and  he  continued  to  discover  fossiliferous  zones 
lower  and  lower  in  the  series.  He  first  designated  these  strata  as  the 
"fossiliferous  graywacke  series,"  but  in  1835  he  changed  this  to  the 
"  Silurian  System,"  named  after  the  Silures,  a  tribe  of  ancient  Britons. 
Sedgwick,  on  the  other  hand,  attempted  the  division  of  the  transition 
series  in  the  Snowdon  district  of  Wales  where  the  complicated  structure 
and  highly  altered  nature  of  the  rocks,  and  consequent  scarcity  of  fossils, 
made  the  problem  an  extremely  difficult  one.  In  1835  he  proposed  the 
name  "  Cambrian  Series  "  for  the  lower,  older  member,  taking  the  name 
from  Cambria,  the  Roman  name  for  northern  Wales. 

Murchison  divided  his  Silurian  system  into  an  upper  and  lower  portion 
which  were  separated  from  each  other,  as  pointed  out  by  Sedgwick,  by  an 
angular  unconformity  marking  the  boundary  between  the  Caradoc  and  the 
Llandovery  groups.  The  lower  limit  of  his  Silurian  was  not  defined,  but 
he  finally  included  all  of  the  fossiliferous  strata  of  Sedgwick's  Cambrian. 

Murchison.  in  his  volume  on  the  Silurian  system  published  in  1839, 
recognized  the  Cambrian  series,  and  up  to  this  point  the  two  workers 
agreed.  However,  in  1842,  in  his  presidential  address  to  the  Geological 
Society  of  London,  he  stated  that  the  Cambrian  fossils  did  not  differ  from 


26        THE  CAMBRIAN  AND  ORDOVICIAN  DEPOSITS  OF  MARYLAND 

those  of  the  Lower  Silurian,  an  opinion  eminently  correct  because,  as  just 
noted,  he  had  included  in  it  all  of  the  fossiliferous  Cambrian.  In  the 
publication  of  his  Siluria  several  years  later,  Murchison  still  regarded 
Sedgwick's  Cambrian  system  as  simply  a  local  facies  of  the  Silurian 
system.  The  historic  but  unfortunate  controversy  on  this  question  now 
ensued.  Murchison,  by  means  of  his  influential  official  and  social  position, 
was  able  to  dominate  the  subject  and  most  of  the  rocks  now  recognized 
as  Cambrian,  Ordovician,  and  Silurian  were  marked  Silurian  on  the 
British  geological  maps,  and  in  both  America  and  Europe  fossils  collected 
from  the  equivalent  of  the  "  Transition  Series  "  were  almost  invariably 
classed  as  Silurian.  The  term  Cambrian  was  practically  discarded 
because,  according  to  Murchison,  it  was  impossible  to  recognize  the  strata 
on  account  of  their  supposed  lack  of  characteristic  fossils. 

Tn  1879  Professor  Lapworth  of  Birmingham  University,  England, 
proposed  that  Murchison's  term  Lower  Silurian  be  replaced  by  the  name 
Ordovician,  after  the  Ordovices,  a  tribe  which  lived  in  Wales  at  the  time 
of  the  Romans.  Sedgwick  in  his  writings  continued  to  insist  that  the 
Cambrian  system  was  an  independent  group  of  rocks  and  proposed  to 
limit  the  Silurian  to  the  Ludlow  and  the  Wenlock,  with  the  Mayhill  sand- 
stone at  the  base.  In  his  introduction  to  Salter's  Catalogue  of  Cambrian 
and  Silurian  fossils,  published  in  1873,  the  year  of  his  death,  he  held  to 
this  same  view.  As  practically  all  of  the  faunas  which  he"  considered  as 
Cambrian  and  the  main  mass  of  the  rocks  included  by  him  in  the  Cam- 
brian system  are  now  recognized  as  typical  Ordovician,  it  is  evident  that 
the  present-day  usage  of  the  term  Cambrian  does  not  follow  the  intentions 
of  its  author.  The  upper,  typical  portion  of  the  Silurian  system,  to 
which  the  name  Silurian  was  restricted  when  Lapworth  introduced  the 
new  name  Ordovician  for  the  Lower  Silurian,  was  named  Murchisonian 
by  d'Orbigny  in  1850,  but  this  term  never  received  a  wide  acceptance. 

With  the  adoption  of  the  terms  Ordovician  and  Silurian  by  many 
geologists  the  name  Cambrian  was  finally  retained  for  the  lower,  much 
more  sparingly,  unfossiliferous  rocks  of  the  original  Cambrian  of  Sedg- 
wick— a  most  unfair  procedure  and  one  to  which  that  author  objected 


MARYLAND  GEOLOGICAL  SURVEY  27 

vigorously  in  his  lifetime.  Still  another  classification  of  pre-Devonian 
Paleozoic  rocks  is  that  of  De  Lapparent  who  recognized  the  Silurian  for 
the  entire  interval,  with  the  three  divisions — ;Cambrian,  Ordovician,  and 
Bohemian  or  Gothlandian. 

Another  term  which  enters  into  this  controversy  is  that  of  the  Taconic 
system.  The  Taconic  question  was  the  basis  of  a  controversy  in  America 
similar  to  that  of  the  Silurian  in  Great  Britain.  In  1838  Emmons  noted 
that  the  Potsdam  sandstone  was  the  oldest  sedimentary  rock  in  the 
vicinity  of  Potsdam,  New  York,  as  it  here  rested  upon  pre-Paleozoie 
crystallines,  an  observation  still  recognized  as  correct.  Overlying  the 
Potsdam  sandstone,  he  found  the  Calciferous  sandrock,  the  Chazy,  Birds- 
eye,  and  Trenton  limestones,  and  the  Utica  and  Hudson  Kiver  shales. 
In  western  Massachusetts  at  the  foot  of  the  Hoosac  Mountains  he  found 
an  entirely  different  series  resting  directly  upon  the  gneiss.  Emmons 
believed  this  series  to  be  older  than  the  Potsdam  and  in  1841  he  applied 
to  it  the  name  Taconic  system,  after  the  Taconic  range.  The  controversy 
which  arose  over  the  reality  of  his  system  lasted  over  half  a  century,  and 
although  Emmons  defended  his  opinion  until  the  day  of  his  death, 
stratigraphic  geology  had  then  not  proceeded  far  enough  to  recognize  the 
real  value  of  the  Taconic  rocks  in  classification.  It  is  now  known  that 
the  greater  portion  of  the  Taconic  is  of  Cambrian  age.  With  slight 
emendations  the  term  Taconic  could  in  all  fairness  have  been  recognized 
for  the  Cambrian  or  for  a  portion  of  it  just  as  Sedgwick's  term  Cambrian 
should  have  been  applied  to  the  rocks  now  called  Ordovician. 

During  the  quarter  of  a  century  or  more  following  Lapworth's  defini- 
tion of  the  Ordovician  system  and  the  recognition  in  America  of  the 
Cambrian,  Ordovician,  and  Silurian,  with  the  limits  generally  accepted 
to-day,  no  controversial  matters  of  especial  importance  arose  in  Early 
Paleozoic  stratigraphy.  Most  students  of  the  subject  believed  that  Early 
Paleozoic  sedimentation  took  place  in  quiet  continental  seas  which  were 
often  of  considerable  depth.  It  was  thought  that  sedimentation  endured 
without  interruption  either  through  a  single  period  or  sometimes  through 
several  periods,  until  finally  there  was  land  elevation  and  withdrawal  of 


28        THE  CAMBRIAN  AND  ORDOVICIAN  DEPOSITS  or  MARYLAND 

the  sea.  Then  after  extensive  erosion,  the  sinking  of  the  land  and  incur- 
sion of  the  sea  inaugurated  another  period  of  geological  history.  Faunal 
differences  in  apparently  contemporaneous  strata  were  attributed  to  the 
different  habitats  of  the  organisms,  while  the  absence  of  certain  strata 
over  wide  areas  was  explained  by  the  erosion  during  the  land  interval. 
The  great  changes  in  lithological  character  from  place  to  place  depended 
upon  the  topography  of  the  land  masses  bordering  the  continental  seas. 

In  the  last  decade  so  many  new  stratigraphic  and  paleontologic  facts 
have  come  to  light  that  the  old  conceptions  regarding  stratigraphic  corre- 
lation and  the  ideas  concerning  the  character  and  extent  of  the  ancient 
continental  seas  have  been  greatly  modified  and  .often  discredited.  The 
lifelong  studies  of  E.  0.  Ulrich  upon  the  stratigraphy  and  paleontology 
of  the  American  Paleozoic  have  brought  to  light  new  criteria  for  systemic 
delimitation,  and  caused  him  to  propose  a  revision  of  the  Paleozoic  sys- 
tems based  upon  these  new  conceptions.  According  to  his  views  there 
never  was  a  vast  continental  sea  of  considerable  depth  enduring  through  any 
great  period  of  deposition,  nor  was  there  ever  any  considerable  elevation  of 
the  adjacent  land  masses  with  the  consequent  erosion,  except  for  compara- 
tively brief  periods.  In  his  work  in  collaboration  with  Professor  Charles 
Schuchert,  published  in  Bulletin  52  of  the  New  York  State  Museum 
under  the  title  "  Paleozoic  seas  and  barriers  in  eastern  North  America/' 
it  was  brought  out  that  the  diastrophic  movements  producing  deformation 
of  the  land  masses,  manifested  themselves  not  only  between  the  larger 
divisions  of  geologic  time,  but  even  between  formations.  These  move- 
ments resulted  in  a  north  and  south  warping  of  the  continent  with  the 
formation  of  narrow  structural  troughs  whose  position  was  determined 
by  their  location  in  areas  with  a  predisposition  to  sink.  These  troughs 
or  negative  areas  were  separated  more  or  less  completely  by  anticlinal 
areas  which  had  a  positive  tendency  to  remain  above  sea  level  in  all  except 
the  periods  of  most  general  submergence. 

These  positive  and  negative  areas  were  discussed  in  more  detail  by 
Schuchert  in  his  great  work  on  the  Paleogeography  of  North  America, 
published  in  1910  in  the  Bulletin  of  the  Geological  Society  of  America. 


29 

The  positive  areas  were  seldom  elevated  enough  to  have  great  erosive 
activity  and  the  land  masses  were  generally  quite  low.  As  a  result  there 
are  certain  limestone  formations  which  hold  their  lithologic  character  for 
hundreds  of  miles. 

In  his  epoch-making  work  on  the  Eevision  of  the  Paleozoic  Systems, 
published  in  volume  22  of  the  Bulletin  of  the  Geological  Society  of 
America,  in  1911,  Ulrich  has  given  a  very  detailed  account  of  the  dia- 
strophic  and  faunal  criteria  employed  by  him  in  his  studies  on  strati- 
graphic  classification,  and  he  has  devoted  much  attention  to  the  oscillatory 
character  of  continental  seas.  The  northeast-southwest  troughs,  separated 
by  barriers  or  areas  around  which  warping  took  place,  were  invaded  by  the 
sea  many  times  during  the  course  of  a  period.  Other  barriers  or  areas 
extending  at  approximate  right  angles  to  these  troughs,  separated  them 
into  basins.  The  general  idea  was  that  the  sea  advanced  and  retreated 
many  times  during  the  course  of  a  period  within  these  comparatively 
restricted  basins.  With  each  successive  invasion  sediments  were  deposited 
over  a  larger  area  so  that  the  final  result  was  a  series  of  overlapping 
deposits  thinning  out  on  the  sides  of  the  trough.  Each  trough  or  basin 
would  contain  series  of  formations  marked  off  by  diastrophic  and  faunal 
evidence  and  a  formation  would  be  lithologically  and  f aunally  similar  only 
in  its  own  basin,  except  in  periods  of  great  submergence  when  the  sea 
advanced  over  the  barriers.  As  the  different  basins  of  sedimentation  at 
times  connected  with  different  oceanic  areas,  the  marine  forms  of  life  in 
them  would  consequently  be  different.  Therefore,  formations  of  the 
same  age  in  adjoining  basins  may  differ  totally  not  only  in  their  lithologic 
characters,  but  also  in  their  faunal  contents.  These  troughs  of  deposition, 
with  their  separating  barriers,  were  greatly  influenced  by  later  and  later 
periods  of  diastrophism  with  the  result  that  in  the  Appalachians,  where 
folding  occurred,  the  barrier  or  anticlinal  structure  is  now  much  dimin- 
ished in  width  and  is  often  represented  by  an  overthrust  fault. 

In  addition  to  the  north  and  south  structural  lines  it  has  been  found 
that  there  were  definite  east  and  west  lines  or  axes  which  serve  as  pivots 
of  oscillation  for  the  continent.  The  formations  thin  from  either  side 


30        THE  CAMBRIAN  AND  ORDOVICIAN  DEPOSITS  OF  MARYLAND 

along  these  lines  just  as  in  the  north  and  south  structural  troughs  they 
thin  along  the  edges  of  the  trough. 

The  greatest  sea  withdrawal  marks  the  systemic  boundaries,  but  the 
advance  and  retreat  of  the  seas  within  the  systems  would  naturally  not  be 
uniform  throughout  the  basins  of  deposition.  Therefore  one  area  will 
have  deposits  which  are  represented  in  another  area  by  a  stratigraphic 
hiatus.  As  a  result  of  this,  the  complete  section  cannot  be  found  at  any 
one  place  but  it  is  a  composite  one  made  up  of  units  from  many  places. 
The  disregard  of  this  fact  has  delayed  the  recognition  of  many  new 
formations  heretofore,  as  in  the  case  of  the  so-called  Ozarkian. 

Under  the  conception  of  little  elevation  and  often  slight  erosion  of  the 
Eopaleozoic  land  masses,  the  stratigraphic  unconformities  are  not  strongly 
marked  even  though  the  time  interval  may  have  been  great.  The  bedding 
planes  of  strata  belonging  to  distinct  formations  are  usually  parallel  and 
the  detection  of  such  unconformities  is  most  difficult.  The  f aunal  method 
of  discrimination  is  a  sure  one,  provided  the  occurrence  and  range  of  the 
faunas  are  well  known.  Another  method  is  in  the  comparison  of  detached 
sections  and  noting  the  gradual  interpolation  of  other  strata  between  two 
formations  with  persistent  lithologic  characters.  In  the  discrimination 
of  the  Ordovician  rocks  of  Maryland,  this  latter  method  is  extremely 
useful,  as  several  of  the  formations  developed  in  states  to  the  north  and 
south  are  represented  here  only  by  their  overlapping  margins. 

In  the  classification  of  Paleozoic  rocks,  as  commonly  recognized,  the 
Cambrian  and  Ordovician  systems  forming  the  subject  of  this  volume 
comprise  the  Eopaleozoic.  In  his  revision  of  the  Paleozoic  systems,  Ulrich 
has  proposed  and  defined  two  new  systems,  the  Ozarkian  and  Canadian, 
which  occupy  the  interval  between  a  slightly  restricted  Cambrian  and  a 
more  modified  Ordovician  system.  Brief  descriptions  of  these  new 
systems  were  read  at  the  Baltimore  meeting  of  the  Geological  Society 
of  America  in  1909,  but  were  not  published  until  1911.  In  1910,  in  his 
Paleogeography  of  North  America,  Schuchert  adopted  both  of  the  new 
systems,  crediting  them  to  Ulrich,  and  introduced  a  third  for  the  Cin- 
cinnatian  rocks  hitherto  classified  at  the  top  of  the  Ordovician.  The 


MARYLAND  GEOLOGICAL  SURVEY  .  31 

principles  upon  which  the  Ozarkian  and  Canadian  have  been  founded  are 
discussed  in  great  detail  in  the  Eevision  and  their  author  has  a  mono- 
graphic study  on  their  paleontology  and  stratigraphy  in  the  course  of 
preparation.  Although  each  of  the  new  systems  (Ozarkian  and  Cana- 
dian )  contains  strata  heretofore  in  the  one  case  referred  to  the  underlying 
Cambrian  and  in  the  other  to  the  overlying  Ordovician,  much  the  greater 
part  of  each  system  is  composed  of  thick  formations  whose  actual  dis- 
tinctness from  the  typical  Cambrian  and  Ordovician  has  never  been 
appreciated.  In  short  these  two  systems,  like  the  Cambrian,  Ordovician 
and  all  well-founded  geologic  systems,  are  based  on  a  certain  sequence  of 
diastrophic  events  and  a  sufficient  thickness  of  marine  deposits  to  repre- 
sent a  period  of  geologic  time  approximating  in  length  that  represented  by 
such  other  well-established  systems  as  the  Silurian  and  Devonian.  They 
were  not  founded  primarily  on  fossil  evidence,  but  on  the  physical  criteria 
of  great  series  of  marine  deposits  found  wedging  in  between  the  under- 
lying uneven  top  of  older  formations,  which  contain  the  now  well-known 
and  altogether  characteristic  Upper  Cambrian  fauna,  and  the  similarly 
uneven  base  of  another  system  that  comprises  the  bulk  and  most  char- 
acteristic parts  of  the  Ordovician  system  of  the  literature.  The  fossil 
contents  of  the  two  new  systems  were,  of  course,  immediately  utilized  in 
recognizing  the  several  formations  from  place  to  place.  But  the  Ozarkian 
and  the  Canadian  faunas  as  such  could  be  appreciated  only  after  the 
systems  themselves  had  been  discriminated  by  physical  criteria.  So  far 
as  these  faunas  have  been  worked  out  they  are  clearly  distinguishable  and 
as  different  from  each  other  and  from  the  preceding  Cambrian  and  the 
succeeding  Ordovician  faunas  as  are  the  organic  remains  in  any  succeed- 
ing contiguous  pair  of.  systems.  In  other  words  the  Ozarkian  fauna  as 
shown  in  Ulrich's  collections  in  the  U.  S.  National  Museum  is  more 
radically  different  from  the  life  of  the  Upper  Cambrian  seas  than  is  the 
Silurian  from  the  Ordovician,  the  Devonian  from  the  Silurian,  or  the1 
Mississippian  from  the  Devonian.  The  most  striking  feature  of  the 
difference  between  the  Ozarkian  and  the  Cambrian  is  the  strong  develop- 
ment of  straight  and  curved  cephalopods,  and  numerous  coiled  gastro- 
3 


32        THE  CAMBRIAN  AND  ORDOVICIAN  DEPOSITS  OF  MARYLAND 

pods — types  which,  up  to  the  present,  are  entirely  absent  in  Cambrian 
faunas.  The  Canadian  faunas  introduce  a  wealth  of  graptolites,  true 
orthoids  as  distinguished  from  Billingsellidae  brachiopods,  the  first 
ostracods,  and  the  first  of  the  coiled  cephalopods.  The  Ordovician  fauna 
is  at  once  distinguished  from  the  Canadian  by  the  first  appearance  of 
pelecypods,  the  first  of  the  unquestionable  bryozoans.  and  the  first  true 
crinoids. 

The  following  table  is  introduced  to  illustrate  graphically  the  various 
usages  of  the  Silurian  and  related  terms  concerned  in  this  volume : 

Although  the  list  of  papers  dealing  with  the  geology  of  the  parts  of 
Maryland  concerned  in  this  volume  is  quite  lengthy,  the  number  of 
students  whose  observations  have  advanced  the  knowledge  of  the  strati- 
graphy and  paleontology  of  the  region  is  comparatively  small. 

In  1885,  Mr.  H.  R.  Geiger  began  the  study  of  the  Paleozoic  rocks 
along  the  Potomac  River  in  western  Maryland  and  West  Virginia  and 
in  1886  and  1887  extended  his  work  eastward  down  the  Potomac  River 
and  for  some  distance  southward  over  the  Great  Valley  region  of  Virginia. 
In  1888  he  began  work  on  the  Harper's  Ferry  quadrangle  and  after 
several  months  study  came  to  certain  conclusions  regarding  the  relations 
of  the  sandstones  and  associated  formations  in  the  Blue  Ridge  and  South 
Mountain  to  the  limestones  of  the  Great  Valley  which  are  not  held  to-day. 

In  1890  Mr.  Arthur  Keith  undertook  a  reexamination  of  the  Harper's 
Ferry  quadrangle  and  as  a  preliminary  result  of  his  studies  read  a  paper 
in  joint  authorship  with  Mr.  H.  R.  Geiger,  before  the  Geological  Society 
of  America  on  "  The  Structure  of  the  Blue  Ridge  near  Harper's  Ferry." 1 
The  next  year  he  published  a  short  notice  on  "  The  Geologic  Structure  of 
the  Blue  Ridge  in  Maryland  and  Virginia,"  *  and  his  final  results  appeared 
in  the  Harper's  Ferry  folio  No.  10,  Geologic  Atlas  of  the  United  States. 

In  1892  Mr.  Charles  D.  Walcott  made  an  examination  of  the  Blue 
Ridge  and  South  Mountain  region  and  definitely  determined  the  Cam- 
brian age  of  its  quartzites.  A  statement  of  the  results  of  this  investigation 

1  Bull.  Geol.  Soc.  America,  vol.  ii,  1891,  pp.  155-164,  pis.  iv,  v. 
3  American  Geologist,  vol.  x,  1892,  pp.  362-368. 


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34        THE  CAMBRIAN  AND  ORDOVICIAN  DEPOSITS  OF  MARYLAND 

was  set  forth  in  two  papers,  one  entitled  "  Notes  on  the  Cambrian  Bocks 
of  Pennsylvania  and  Maryland  from  the  Susquehanna  to  the  Potomac,"  * 
and  the  other  "  The  Geologist  at  Blue  Mountain,  Maryland."  2 

Mr.  Keith  continued  his  studies  of  South  Mountain  and  Blue  Kidgc 
geology  into  Virginia  and  in  1894  published  a  report  on  the  "  Geology 
of  the  Catoctin  Belt."'  This  report  describes  the  Blue  Eidge,  South 
Mountain,  and  Catoctin  belts -from  northern  Virginia  through  Maryland 
into  Pennsylvania  and  was  an  important  addition  to  the  geologic  knowl- 
edge of  this  area  east  of  the  Great  Valley. 

The  discovery  of  fossils  in  the  Frederick  Valley  limestone  was  an- 
nounced by  Charles  R.  Keyes  in  1890  4  in  an  article  in  which  he  included 
a  geologic  section  across  the  valley.  The  next  contribution  in  which  fossils 
were  mentioned  was  by  Charles  S.  Prosser  in  1900,5  who  described  the 
Shenandoah  limestone  and  Martinsburg  shale  in  a  general  way. 

The  most  important  contributions  to  the  early  Paleozoic  stratigraphy 
of  this  region  appeared  in  1910  in  the  description  of  the  Mercersburg-- 
Chambersburg  district  of  Pennsylvania  by  George  W.  Stose8  in  which 
E.  0.  Ulrich  collaborated  in  the  study  of  the  Shenandoah  limestone  and 
Martinsburg  shale.  Further  stratigraphic  and  paleontologic  details  of 
these  rocks  were  given  by  E.  0.  Ulrich  in  his  "  Revision  of  the  Paleozoic 
System  "  in  19.11/ 

BIBLIOGRAPHY 

1788 

JEFFERSON,  THOMAS.  Notes  on  the  State  of  Virginia.  Phila.,  1788. 
Sm.  8vo.  244  pp. 

The  author  gives  many  interesting  facts  and  speculations  concerning  the  geology 
about  Harper's  Ferry.  Fully  ten  editions  of  this  book  were  published  in  different 
places  between  1782  and  1832,  each  with  different  number  of  pages. 

1  Amer.  Jour.  Sci.,  3d  series,  vol.  xliv,  pp.  469-482. 

2  Nat.  Geog.  Mag.,  vol.  v,  pp.  84-88;  Sci.  Am.  Supp.,  vol.  xxxvii,  pp.  14753-14754. 

3  Fourteenth  Ann.  Rep.  U.  S.  Geol.  Surv.,  part  ii,  1894,  pp.  285-395,  pis.  xix- 
xxxix. 

4  Johns  Hopkins  University  Circular  No.  84,  vol.  x,  1890,  p.  32. 

5  Journal  Geology,  vol.  viii,  pp.  655-663,  figs.  1-4. 
8  U.  S.  Geol.  Survey,  Geol.  Atlas  No.  170,  1910. 

1  Bull.  Geol.  Soc.  America,  vol.  xxii,  No.  3,  pp.  281-680,  5  pis.,  1911. 


MARYLAND  GEOLOGICAL  SURVEY  35 

1809 

MACLURE,  WM.  Observations  on  the  Geology  of  the  United  States, 
explanatory  of  a  Geological  Map.  (Eead  Jan.  20,  1809.) 

Trans.  Amer.  Phil.  Soc.,  o.  s.  vol.  vi,  1809,  pp.  411-428. 
Broad  correlations  and  generalizations  only. 

1814 

MITCHILL,  SAML.  L.  A  Sketch  of  the  Scenery  in  the  region  around 
Harper's  Ferry  where  the  ridge  of  the  Blue  Mountains  is  penetrated  by 
the  joint  waters  of  the  Potomac  and  Shenandoah  rivers.  In  a  letter  to  the 
editor;  dated  Harper's  Ferry,  July  4,  1812.  Bruee's  Amer.  Min.  Jour., 
vol.  i,  Xew  York,  1814.  pp.  211-218. 

The  author  discusses  the  geology  and  stratigraphy  along  the  Potomac  between  Har- 
per's Ferry  and  Washington  and  regards  the  slates  as  older  than  the  limestones. 

1817 

MACLURE,  WM.  Observations  on  the  Geology  of  the  United  States  of 
America,  with  some  remarks  on  the  effect  produced  on  the  nature  and 
fertility  of  soils  by  the  decomposition  of  the  different  classes  of  rocks. 
With 'two  plates.  12mo.  Phila.,  1817. 

(Republished  in  1818,  Trans.  Amer.  Phil.  Soc.,  vol.  i,  n.  s.,  pp.  1-91.) 
A  classic  work  giving  many  references  to  the  limits  and  character  of  the  geologi- 
cal formations  in  Maryland.  The  text  and  map  (120  m.  to  the  inch)  represent  the 
Cretaceous  extending  southwest  to  the  Susquehanna  only.  All  land  to  the  southeast 
of  "  Primitive "  is  "  Alluvium "  in  Maryland.  Pages  105-107  deal  especially  with 
Maryland. 

1834 

AIKIN,  WILLIAM  E.  A.  Some  notices  of  the  Geology  of  the  Country 
between  Baltimore  and  the  Ohio  River,  with  a  section  illustrating  the 
superposition  of  the  rocks. 

Amer.  Jour.  Sci.,  vol.  xxvi,  1834,  pp.  219-232,  plate. 

The  most  complete  description  of  the  geology  of  central  and  western  Maryland 
published  up  to  the  time  of  its  appearance. 

DUCATEL,  J.  T.,  and  ALEXANDER,  J.  H.  Report  on  the  Projected 
Survey  of  the  State  of  Maryland,  pursuant  to  a  resolution  of  the  General 
Assembly.  8vo.  39  pp.  and  map.  Annapolis,  1834. 

Maryland  House  of  Delegates,  Dec.  Sess.,  1833,  8vo.,  39  pp. 

Another  edition,  Annapolis,  1834,  8vo.,  58  pp..  and  map. 

Another  edition,  Annapolis,  1834,  8vo.,  43  pp.,  and  folded  table. 

Amer.  Jour.  Sci.,  vol.  xxvii,  1835,  pp.  1-38. 


36        THE  CAMBRIAN  AND  ORDOVICIAN  DEPOSITS  OF  MARYLAND 

Results  of  a  preliminary  survey  of  the  state.  The  area  and  formations  of  the 
state  are  divided  into  three  divisions  corresponding  to  the  present  Coastal  Plain,  Pied- 
mont Plateau  and  Appalachian  areas.  Many  local  descriptions  and  references  are 
given  with  marked  tendency  towards  economic  point  of  view. 

1835 

TAYLOR,  RICHARD  C.  Review  of  Geological  Phenomena  and  the  deduc- 
tions derivable  therefrom  in  two  hundred  and  fifty  miles  of  sections  in 
parts  of  Virginia  and  Maryland. 

Trans.  Geol.  Soc.  Penn.,  vol.  i,  1835,  pp.  314-325  (with  colored  sections). 

The  paper  describes  various  sections,  one  of  which  extends  from  Winchester  to 
Harper's  Ferry  and  thence  east  to  within  30  miles  of  Baltimore.  This  section  is  pi. 
xvii,  fig.  1. 

1841 

DUCATEL,  J.  T.  Annual  Report  of  the  Geologist  of  Maryland,  1840. 
8vo.  46  pp.  (Annapolis,  1840.)  Map  and  sections. 

Another  edition,  8vo.,  59  pp.  and  3  plates,  also  Md.  House  of  Delegates,  Dec. 
Sess.,  1840,  n.  d.,  8vo.,  43  pp.,  3  plates. 

Considers  the  physical  geography  and  geology  of  Allegany  and  Washington  counties, 
with  notes  on  the  copper  mining  about  Frederick. 

1853 

MARCOU,  JULES.  A  Geological  Map  of  the  United  States  and  the 
British  Provinces  of  North  America,  with  an  explanatory  text  (etc.). 
8vo.  Boston,  1853. 

Represents  no  Cretaceous  on  Western  Shore ;  most  of  the  Eastern  Shore  as  Alluvium 
and  the  rest  of  the  state  covered  successively  by  bands  of  Metamorphlc,  New  Red, 
Metamorphic,  Silurian  and  Devonian.  No  Carboniferous  is  represented  within  the 
limits  of  the  state  (?). 

1855 

MARCOU,  J.  Resume  explicatif  d'un  carte  geologique  des  Etats-Unis 
et  des  provinces  anglaises  de  1'Amerique. 

Bull.  Soc.  G4ol.  Fr.,  2  ser.,  tome  xii,  1855,  pp.  813-936;  colored  geological  map. 
Explanation    of    map    itself,    so   far   as    related    to    Maryland,    apparently    based    on 
Maclure. 

1856 

HITCHCOCK,  E.  Outline  of  the  Geology  of  the  Globe  and  of  the  United 
States  in  particular,  with  geological  maps,  etc.  8vo.  Boston,  1856. 
(3ded.) 

In  discussing  the  areal  distribution  of  the  different  formations  he  frequently  men- 
tions Maryland,  giving  reasons  for  location  of  the  lines  on  his  maps. 


MARYLAND  GEOLOGICAL  SURVEY  37 

1858 

ROGERS,  H.  D.  The  Geology  of  Pennsylvania.  2  vols.  (Vol.  II  in 
two  parts)  and  maps.  4to.  Phila.,  1858. 

This  work  containing  frequent  references  to  the  Maryland  extension  of  formations 
studied  in  Pennsylvania,  besides  giving  the  typical  sections,  terms,  fossils,  etc. 

1860  .   .. 

TYSON,  P.  T.  First  Eeport  of  Philip  T.  Tyson,  State  Agricultural 
Chemist,  to  the  House  of  Delegates  of  Maryland.  Jan.,  1860.  8vo. 
145  pp.  Annapolis,  1860.  Maps. 

Md.  Sen.  Doc.  (E).    Md.  House  Doc.  (C). 

Deals  with  the  rocks  and  soils,  fertilizers,  etc.,  and  explains  the  accompanying 
geological  map. 

1875 

FONTAINE,  WM.  M.    On  some  Points  in  the  Geology  of  the  Blue  Ridge 

in  Virginia. 

Amer.  Jour.  Sci.,  3d  ser.,  vol.  ix,  1875,  pp.  14^22,  93-101.  (Abst.)  Geol.  Record, 
1875,  London,  1877,  p.  119. 

Includes  a  few  notes  on  Catoctin  Mt.,  and  the  argillites  of  Point  of  Rocks  and 
Harper's  Ferry,  pp.  15-17.  The  first  paper  deals  with  some  of  the  general  problems 
involved  in  a  study  of  the  Blue  Ridge,  and  the  illustrations  are  mostly  taken  from 
that  portion  of  the  range,  near  the  Potomac  River.  The  second  paper  deals  with 
the  area  about  Lynchburg  and  southward. 

— .    On  the  Primordial  Strata  of  Virginia. 

Amer.  Jour.  Sci.,  3d  ser.,  vol.  ix,  1875,  pp.  361-369,  416-428,  3  figures. 

(Abst.)  Geol.  Record,  1875,  London,  1877,  p.  119. 

Refers  briefly  to  the  geology  of  Harper's  Ferry  (p.  362)  and  to  the  folds  at 
"Cement  Mill"  near  Hancock  (p.  364).  Geology  of  the  Harper's  Ferry  region,  pp. 
422-423. 

1876 

HUNT,  T.  STERRY.    Geology  of  Eastern  Pennsylvania, 
Proc.  Amer.  Assoc.  Adv.  Sci.,  vol.  xxv,  1876,  pp.  208-212. 

Considers  the  Blue  Ridge  in  Maryland  to  be  Montalban  and  Huronian  with  no 
Laurentian. 

1879 

FRAZER,  PERSIFOR,  JR.  Fossil  (?)  Forms  in  the  Quartzose  Rocks  of 
the  Lower  Susquehanna,  with  plate.  (Read  April  4,  1879.) 

Proc.  Amer.  Phil.  Soc.,  vol.  xviii,  1880,  pp.  277-279. 

Deals  with  some  curious  indeterminate  forms  from  Frazier's  Point,  Cecil  County. 
Letters  by  Whitfleld  and  Hall. 


38        THE  CAMBRIAN  AND  ORDOVICIAN  DEPOSITS  OF  MARYLAND 

1880 
DANA,  J.  D.    Manual  of  Geology.    3d  ed. 

Maryland,  pp.  236,  243,  419,  455,  490,  494-5. 

FRAZER,  PERSIFOR,  JR.    The  Geology  of  Lancaster  County,  Pa. 

Kept.  2d  Geol.  Surv.,  Pa.,  ccc.    Harrisburg,  1880  atlas. 

Deals  with  the  geological  formations  along  the  border  of  the  state  and  their 
extension  into  Maryland. 

LESLEY,  J.  P.  On  a  slab  of  roofing  slate  covered  with  casts  of  Butho- 
trephis  flexuosa  from  the  Peach  Bottom  Slate  Quarries.  (Read  Dec., 
1879.) 

Proc.  Amer.  Phil.  Soc.,  vol.  xviii,  1880,  pp.  364-369. 

This  paper  gives  the  history  of  the  find,  its  determination  by  Lesquereux,  analy- 
sis of  slate  and  remarks  by  Frazer. 

— .  A  Hudson  River  fossil  plant  in  the  roofing  slate  that  is 
associated  with  the  chlorite  slate  and  metamorphic  limestone  in  Mary- 
land, adjoining  York  and  Lancaster  counties,  Pennsylvania. 

Amer.  Jour.  Sci.,  3d  ser.,  vol.  xix,  1880,  pp.  71-72. 

Buthotrephis  flexuosa  (determined  by  Lesquereux)  in  the  Peach  Bottom  slates, 
Silurian  age  inferred.  Extract  from  a  letter. 

1882 

SCHARF,  J.  T.  History  of  Western  Maryland,  being  a  history  of 
Frederick,  Montgomery,  Carroll,  Washington,  Allegany,  and  Garrett 
counties  from  the  earliest  period  to  the  present  day.  2  vols.  4to.  Phila., 
1882.  .  Topography  and  Geology  by  P.  R.  Uhler.  pp.  13-46. 

1884 

FRAZER,  P.,  JR.  The  Peach  Bottom  Slates  of  Southeastern  York  and 
Southern  Lancaster  counties. 

Trans.  Amer.  Inst.  Min.  Eng.,  vol.  xii,  1884,  pp.  355-358.    Plates  and  section. 

(Abst.)  Amer.  Jour.  Sci.,  3  ser.,  vol.  xxix,  1884,  p.  70. 

Discussion  of  a  section  along  the  Susquehanna  River  northward  from  the  Mary- 
land line.  Also  a  letter  from  Prof.  James  Hall  regarding  the  probable  age  of  the 
slates,  which  he  considers  are  either  the  Hudson  River  or  the  Quebec  group  from  the 
presence  of  forms  allied  to  Holymenites,  Lamnantes  lagranger  and  graptolithus. 

ROGERS,  WILLIAM  BARTON.  A  reprint  of  Annual  Reports  and  other 
papers  on  the  Geology  of  the  Virginias.  Sm.  8vo.  Appleton,  1884. 


MARYLAND  GEOLOGICAL  SURVEY  39 

WALLING,  H.  F.  Topographical  Indications  of  a  Fault  near  Harper's 
Ferry. 

(Abst.)  Bull.  Phil.  Soc.,  Washington,  vol.  vi,  1884,  pp.  30-32. 

Mentions  the  discontinuous  extension  of  the  Blue  Ridge  at  Harper's  Ferry  in  sup 
port  of  increased  corrugation  and  steepness  of  dip  eastward  with  reversed  folding. 
The  downthrow  to  the  west. 

1886 

FRAZER,  PERSIFOR,  JR.  General  Notes.  Sketch  on  the  Geology  of 
York  County,  Pennsylvania.  (Read  Dec.  4,  1885.) 

Proc.  Amer.  Phil.  Soc.,  Phila.,  vol.  xxiii,  1886,  pp.  391-410. 
Discussion  of  the  general  structure  equally  applicable  to  Maryland. 

1890 

KEYES,  CHARLES  EOLLIN.     Discovery  of  fossils  in  the  limestone  of 

Frederick  County,  Maryland. 

Johns  Hopkins  Univ.  Cir.  No.  84,  vol.  x,  1890,  p.  32. 

Gives  a  geological  section  and  description  of  Frederick  Valley  and  enumerates 
the  fossils  found  there. 

MACFARLANE,  J.  R.  An  American  Geological  Railway  Guide.  2d  ed. 
8vo.  426  pp.  Appleton,  1890. 

Maryland  notes  based   on   data  from   Uhler,   Williams,   Fontaine   and   Chester. 

1891 

GEIGER,  H.  R.,  and  KEITH,  ARTHUR.  The  Structure  of  the  Blue  Ridge 
near  Harper's  Ferry.  (Read  Dec.,  1890.) 

Bull.  Geol,  Soc.  Amer.,  vol.  ii,  1891,  pp.  155-164,  plates  iv  and  v. 

(Abst.)  Amer.  Geol.,  vol.  vii,  1891,  p.  262;  Amer.  Nat,  vol.  xxv,  1891,  p.  658. 

The  authors  conclude  that  the  sandstones  are  not  Potsdam,  as  previously  considered, 
but  Upper  Silurian.  The  paper  is  accompanied  by  geological  map  and  sections. 

KEYES,  CHARLES  ROLLIN.    Paleozoic  fossils  of  Maryland. 

Johns  Hopkins  Univ.  Cir.  No.  94,  vol.  xi,  1891,  pp.  28-29. 
Enumerates  the  fossils  and  type  localities. 

— .  A  Geologic  Section  across  the  Piedmont  Plateau  in  Maryland. 
Bull.  Geol.  Soc.  Amer.,  vol.  ii,  1891,  pp.  319-322.  (Published  separately,  1890.) 
(Abst.)  Amer.  Geol.,  vol.  viii,  1891,  p.  331. 

Besides  the  general  treatment  of  the  structure  from  Washington  to  Catoctin  Mt., 
there  is  a  very  brief  discussion  of  structure  of  Sugar  Loaf  Mt.  p.  322. 


40        THE  CAMBRIAN  AND  ORDOVICIAN  DEPOSITS  OF  MARYLAND 

WALCOTT,  C.  D.    Correlation  Papers — Cambrian. 
Bull.  U.  S.  Geol.  Surv.,  No.  81,  1891. 
House  Misc.  Doc.,  52d  Cong.,  1st  sess.,  vol.  xx,  No!  25. 

Based  chiefly  on  Tyson's  Repqrt,  pp.  133,  287,  290.  For  problems  unsolved  see 
pp.  328-383. 

1892 

KEITH,  ARTHUR.  The  Geologic  Structure  of  the  Blue  Ridge  in  Mary- 
land and  Virginia. 

Amer.  Geol.,  vol.  x,  1892,  pp.  362-368. 

Broadly  considered,  the  region  is  an  anticline,  where  an  arch  is  crumpled  into 
several  synclines  and  broken  by  faults  till  the  resultant  structure  is  quite  complicated. 

LESLEY,  J.  P.  A  Summary  description  of  the  Geology  of  Pennsylvania. 
3  vols.  Harrisburg,  1892. 

Numerous    references    to    formations    passing    southwards    into    Maryland. 

WALCOTT,  C.  D.    The  Geologist  at  Blue  Mountain,  Maryland. 

Nat.  Geog.  Mag.,  vol.  5,  1892,  pp.  84-88. 

Sci.  Amer.  Supp.,  vol.  37,  1892,  pp.  14753-14754. 

— .     Notes  on  the  Cambrian  Rocks  of  Pennsylvania  and  Mary- 
land from  the  Susquehanna  to  the  Potomac. 

Amer.  Jour.  Sci.,  3d  ser.,  vol.  xliv,  1892,  pp.  469-482. 

The  portion  of  Maryland  studied  lies  in  the  Blue  Ridge  and  Catoctin  mountains  from 
Mechanicstown  (Thurmont)  to  Monterey,  Pa.,  along  the  W.  M.  R.  R.  and  southward  to 
Harper's  Ferry,  W.  Va. 

1893 

WILLIAMS,  G.  H.  (The  Appalachian  Region  and  the  Itinerary  from 
Washington,  D.  C.,  to  Cumberland,  Maryland.) 

Geological  Guidebook  of  the  Rocky  Mt.  Excursion,  Compte  Rendu  de  la  5me 
Ses.  Congres  Geolog.  Internat.  Washington,  1893,  pp.  268-279. 

House  Misc.  Doc.,  53d  Cong.,  2d  sess.,  vol.  xiii,  No.  107,  pp.  268-279. 

Summary  of  the  local  geology  along  the  route. 

WILLIAMS,  G.  H.,  and  CLARK,  W.  B.    Geology  of  Maryland. 

Maryland,  its  Resources,  Industries  and  Institutions,  Baltimore,  1893, 
pp.  55-89. 

A  general  summary  of  the  geology  of  Maryland  with  many  illustrations  and  local 
references. 

WILLIS,  BAILEY.    The  Mechanics  of  Appalachian  Structure. 

13th  Ann.  Rept.  U.  S.  Geol.  Surv.,  1891-92,  pt.  2,  Washington,  1893,  pp.  211-281, 
plates  and  maps. 

The  discussion  includes  illustrations  from  Maryland,  and  its  conclusions  are  appli- 
cable to  the  western  portion  of  the  state. 


MARYLAND  GEOLOGICAL  SURVEY  41 

1894 

KEITH,  ARTHUR.    Geology  of  the  Catoctin  Belt. 

14th  Ann.  Kept.  U.  S.  Geol.  Surv.,  1892-93,  Washington,  1894,  pt.  ii,  pp.  285-395, 
maps  and  plates. 

House  Exec.  Doc.,  53d  Cong.,  2d  sess.,  vol.  xvii,  p.  285. 
(Rev.)  Sciences,  n.  s.,  vol.  ii,  1895,  p.  97. 
A  full  discussion  of  the  area  studied. 

— .     Harper's  Ferry  Folio,  Explanatory  Sheets. 

U.  S.  Geol.  Surv.  Geol.  Atlas,  folio  No.  10,  Washington,  1894. 
Brief  epitomized  discussion  of  the  local  geology,  structure  and  geological  history  of 
the  area  included. 

1896 

DORSEY,  CLARENCE  W.    The  Soils  of  the  Hagerstown  Valley. 

Md.  Agr.  Exp.  Sta.  Bull.  No.  44,  College  Park,  1896. 

A  study  of  the  soils  resulting  from  the  disintegration  of  the  Cambrian  sandstone, 
Hudson  River  shales  and  Trenton  limestones.  Distinguished  five  types. 

WALCOTT,  C.  D.    The  Cambrian  Rocks  of  Pennsylvania. 

Bull.  U.  S.  Geol.  Surv.  No.  134,  1896. 
House  Misc.  Doc.,  54th  Cong.,  2d  sess.,  No.  24. 

Contains  incidental  reference  to  his  work  with  Keith  in  Frederick  County  and  also 
to  the  southern  continuation  of  Pennsylvania  formations. 

WILLIS,  BAILEY.    The  Northern  Appalachians. 

The  Physiography  of  the  United  States. 

Geographic  Monographs  I,  American  Book  Company,  169  pp.,  1896. 

A  study  of  the  present  topography  and  its  origin. 

1897 

CLARK,  WILLIAM  BULLOCK.  Historical  sketch  embracing  an  account 
of  the  progress  of  investigation  concerning  the  physical  features  and 
natural  resources  of  Maryland. 

Md.  Geol.  Surv.,  vol.  i,  pp.  43-138,  pis.  ii-v,  1897. 

— .  Outline  of  present  knowledge  of  the  physical  features  of 
Maryland,  embracing  an  account  of  the  physiography,  geology,  and 
mineral  resources. 

Md.  Geol.  Surv.,  vol.  i,  pp.  141-228,  pis.  vi-xiii,  1897. 

Description  of  the  physiographic  features  of  the  state,  the  character  and  distribution 
of  the  igneous  and  sedimentary  rocks,  and  the  mineral  resources. 


42        THE  CAMBRIAN  AND  ORDOVICIAN  DEPOSITS  or  MARYLAND 

1899 

ABBE,  CLEVELAND,  JR.  A  general  report  on  the  physiography  of  Mary- 
land. 

Md.  Weather  Service,  vol.  i,  pp.  41-216,  pis.  iii-xix,  figs.  1-20,  1899. 
Discusses    the    physiographic    features    of    the    Piedmont    Plateau    and    Appalachian 
provinces  in  Maryland. 

CLARK,  WILLIAM  BULLOCK.  The  relations  of  Maryland  topography, 
climate,  and  geology  to  highway  construction. 

Md.  Geol.  Surv.,  vol.  iii,  pp.  47-106,  pis.  iii-xi,  figs.  1-3, 1899. 

1900 

PROSSER,  CHARLES  S.  The  Shenandoah  limestone  and  Martinsburg 
shale. 

Jour.  Geol.,  vol.  viii,  pp.  655-663,  figs.  1-4,  1900. 

Describes  the  lithologic  and  faunal  characters  of  the  formations  In  adjacent  portions 
of  Maryland  and  West  Virginia. 

ULRICH,  E.  0.,  and  SCHUCHERT,  CHARLES.  Paleozoic  Sjas  and  barriers 
in  eastern  North  America. 

N.  Y.  State  Mus.,  Bull.  No.  52,  pp.  633-663,  1  pi. 

1906 

CLARK,  WILLIAM  BULLOCK.  Report  on  the  physical  features  of  Mary- 
land, together  with  an  account  of  the  exhibits  of  Maryland  mineral 
resources  made  by  the  Maryland  Geological  Survey. 

Maryland  Geol.  Survey  (Special  Publications,  vol.  vi,  pts.  1  and  2),  284  pp., 
30  pis.,  19  figs.,  geol.  map.  (in  pocket),  1906. 

A  general  account  of  the  physiography,  geology  and  mineral  resources  of  the  state. 

1907 

MARYLAND  GEOLOGICAL  SURVEY. 

(Geological)  map  of  Maryland,  prepared  by  Maryland  Geological  Survey, 
Wm.  Bullock  Clark,  State  Geologist,  1907,  Scale  1 :  187,  500. 

BASSLER,  BAY  S.    Cement  and  cement  materials  (of  Virginia). 
In  Watson,  T.  L.,  Mineral  Resources  of  Virginia,  pp.  86-167,  10  pis.,  14  figs., 
1907. 


MARYLAND  GEOLOGICAL  SURVEY  43 

1908 

STOSE,  GEORGE  W.    The  Cambro-Ordovician  limestones  of  the  Appa- 
lachian Valley  in  southern  Pennsylvania. 
Jour.  Geology,  vol.  xvi,  No.  8,  pp.  698-914,  1908. 

BASSLER,  KAY  S.    Cement  materials  of  Western  Virginia. 
Econ.  Geology,  vol.  iii,  No.  6,  pp.  503-524,  4  figs.,  1908. 

PEABODY,  CHARLES.  The  exploration  of  Bushey  cavern,  near  Cave- 
town,  Maryland. 

Phillips  Academy,  Andover,  Massachusetts,  Dept.  of  Archaeology,  Bull,  iv, 
pt.  1,  pp.  3-25,  8  pis.,  1908. 

1909 

MATHEWS,  EDWARD  BENNETT,  and  GRASTY,  JOHN  SHARSHALL.  Ee- 
port  on  the  limestones  of  Maryland,  with  special  reference  to  their  use  in 
the  manufacture  of  lime  and  cement. 

Maryland  Geol.  Survey,  vol.  viii,  pp.  225-477,  14  pis.,  12  figs.,  1909. 

BASSLER,  KAY  S.  The  Cement  Resources  of  Virginia  west  of  the  Blue 
Kidge. 

Virginia  Geol.  Surv.,  Bull  No.  2A,  309  pp.,  30  pis.,  30  figs.,  1909. 

1910 

SCHUCHERT,  CHARLES.    Paleogeography  of  North  America. 
Geol.  Soc.  America  Bull.,  vol.  xx,  pp.  427-606,  56  pis. 

STOSE,  GEORGE  W.  Description  of  the  Mercersburg-Chambersburg  dis- 
trict, Pennsylvania. 

U.  S.  Geological  Survey,  Geol.  Atlas  U.  S.,  Mercersburg-Chambersburg  folio 
(No.  170),  library  edition,  19  pp.,  8  pis.  (maps,  sections,  and  illustrations 
sheets),  5  figs.,  1909;  field  edition,  144  pp.,  6  folded  maps,  10  pis.,  4  figs.,  1910. 

Describes  the  topographic  features,  the  general  geology,  the  occurrence,  character, 
and  relations  of  pre-Cambrian  volcanic  rocks,  and  of  Cambrian,  Ordovician,  Silurian 
and  Devonian  formations,  and  geologic  structure,  the  geologic  history,  and  the  economic 
resources. 

1911 

ULRICH,  EDWARD  0.    Revision  of  the  Paleozoic  Systems. 
Geol.  Soc.  America,  Bull.  vol.  xxii,  No.  3,  pp.  281-680,  5  pis. 


44        THE  CAMBRIAX  AND  ORDOVICIAN  DEPOSITS  OF  MARYLAND 


EATON,  H.  N.  The  geology  of  South  Mountain  at  the  junction  of 
Berks,  Lebanon,  and  Lancaster  counties,  Pennsylvania. 

Jour.  Geology,  vol.  xx,  No.  4,  pp.  331-343,  2  figs.,  May-June,  1912. 
Describes  the  occurrence,  character  and  relation  of  pre-Cambrian,   Cambrian,   Ordo- 
vician  and  Triassic  strata  and  the  structural  conditions. 

JANDORF,  MORTON  LEHMAYER.  Preliminary  report  on  the  York  Valley 
limestone  belt  in  York  County. 

Pennsylvania  Topog.  and  Geol.  Survey,  Kept.  1910-1912,  pp.  50-129,  14  pis. 
(incl.  maps),  1912. 

MOORE,  ELWOOD  S.  Siliceous  oolites  and  other  concretionary  structures 
in  the  vicinity  of  State  College,  Pennsylvania. 

Jour.  Geology,  vol.  xx,  No.  3,  pp.  259-269,  7  figs.,  April-May,  1912:  Abstract, 
British  Assoc.  Adv.  Sci.,  Kept.  81st  Meeting,  p.  390,  1912. 

Describes  the  occurrence  and  geologic  relations  and  discusses  the  origin  of  siliceous 
oolites. 

STOSE,  GEORGE  W.,  and  SWARTZ,  CHARLES  K.  Description  of  the 
Pawpaw  and  Hancock  quadrangles  (Maryland-West  Virginia-Pennsyl- 
vania). 

U.  S.  Geol.  Survey,  Geol.  Atlas  U.  S.  Pawpaw-Hancock  folio  (No.  179),  24  pp., 
11  figs.,  9  pis.  (maps,  sections,  and  illustrations),  1912;  field  edition,  176  pp., 
11  figs.,  20  pis.,  6  folded  maps  (in  pocket),  1912. 

Abstract,  Washington  Acad.  Sci.  Jour.,  vol.  ii,  No.  16,  p.  410,  October  4,  1912. 

Describes  the  topography,  the  character,  occurrence,  and  relations  of  Cambrian, 
Ordovician,  Silurian,  Devonian,  and  Carboniferous  formations,  and  of  Tertiary,  and 
Quaternary  deposits,  the  geologic  structure,  the  geologic  history,  and  the  mineral 
resources. 

WILLIS,  BAILEY.    Index  to  the  stratigraphy  of  Xorth  America. 

U.  S.  Geological  Survey,  Prof.  Paper,  71,  894  pp.,  1  pi.  (geological  map  in  4 
sheets  in  separate  case). 

Brief  notes  on  Maryland  stratigraphy  are  given  in  the  compilation  of  data  used 
in  the  preparation  of  the  geologic  map  of  North  America. 

1913 

BROWN,  THOMAS  C.  Notes  on  the  origin  of  certain  Paleozoic  sedi- 
ments, illustrated  by  the  Cambrian  and  Ordovician  rocks  of  Center 
County,  Pennsylvania. 

Jour.  Geology,  vol.  xxi,  No.  3,  pp.  232-250,  7  figs.,  1913;  (Abst.),  Geol.  Soc. 
America,  Bull.  vol.  xxiv,  No.  1,  p.  112,  March  24,  1913. 

Discusses  the  origin  of  conglomerates,  oolites,  and  sandstones  of  Ordovician  and 
Cambrian  age. 


MARYLAND  GEOLOGICAL  SURVEY  45 


The  subject  of  ancient  or  geologic  geography  for  which  the  term 
"  paleogeography "  was  proposed  in  1872  by  T.  Sterry  Hunt  and  was 
prominently  employed  by  Robert  Etheridge,  the  English  paleontologist, 
in  1881,  has  become  such  an  important  branch  of  stratigraphic  geology 
that  to-day  no  general  stratigraphic  discussion  is  complete  without  an 
attempt  to  indicate  the  distribution  of  the  land  and  water  of  the  time. 
Since  1896  when  Canu  published  his  "  Essai  de  paleogeographie  "  the 
term  has  been  frequently  employed. 

Paleogeographie  maps  have  been  prepared  in  America  since  1863  when 
James  D.  Dana  published  several  generalized  sketches  of  the  Azoic, 
Cretaceous,  and  early  Tertiary  periods,  in  the  first  edition  of  his  Manual 
of  Geology.  Since  then  over  500  paleogeographie  maps  have  appeared, 
about  one-half  of  which  refer  to  North  America.  Until  recent  years  most 
of  these  maps  were  subject  to  the  criticism  that  they  covered  too  much 
time  and  therefore  were  too  generalized. 

Schuchert,  in  1908,  in  his  "  Paleogeography  of  North  America,"  pub- 
lished a  series  of  maps  based  upon  the  most  precise  correlations  and  the 
narrowest  time  limits  that  had  hitherto  been  attempted.  This  work, 
which  was  prepared  in  collaboration  Avith  all  the  leading  American 
stratigraphers  and  paleontologists,  brought  out  with  excellent  clearness 
many  new  features,  especially  the  oscillatory  nature  of  the  continental 
seas.  This  publication  marks  a  great  'advance  in  the  science  of  paleo- 
geography. In  spite  of  efforts  to  the  contrary,  some  of  these  maps,  as  was 
recognized  by  their  author,  covered  too  long  a  time  period,  and  are  subject 
to  the  criticism  just  mentioned. 

Since  1908  a  great  amount  of  new  data  on  the  stratigraphy  and 
paleontology  of  American  early  Paleozoic  formations  has  been  accu- 
mulated and  to-day  maps  covering  the  geography  of  a  single  formation  are 
possible.  Maps  illustrating  the  early  Paleozoic  divisions  of  the  geological 
column  were  prepared  by  E.  0.  Ulrich  and  revised  at  frequent  intervals 
as  new  facts  were  obtained.  But  few  of  these  have  hitherto  been  pub- 
lished, but  the  writer  has  obtained  permission  to  reproduce  in  this  volume 


46        THE  CAMBRIAN  AND  ORDOVICIAN  DEPOSITS  OF  MARYLAND 

all  of  the  maps  covering  the  formations  here  under  discussion.  These 
are  inserted  in  their  appropriate  place  in  the  text. 

It  must  be  remembered  that  in  these  maps  the  shore  lines  are  more  or 
less  hypothetical  and  do  not  show  the  bays  and  other  features  of  present- 
day  strands.  It  must  also  be  remembered  that  the  present-day  base  maps 
do  not  accurately  represent  the  continents  of  past  times,  because  the  latter, 
especially  in  the  mountainous  areas,  have  suffered  great  compression. 

Although  it  is  evident  that  the  portion  of  Maryland  covered  by  the 
Cambro-Ordovician  rocks  is  too  small  a  part  of  the  North  American 
continent  to  reveal  much  of  the  paleogeography,  still  it  may  be  noted 
from  the  accompanying  maps  that  western  Maryland  has  been  much 
concerned  in  the  continental  oscillation  and  other  earth  movements  which 
occasioned  the  repeated  invasions  and  withdrawals  of  the  sea.  In  order 
to  plot  these  sea  invasions  not  only  must  the  distribution  of  the  marine 
sediments  of  the  time  be  determined  and  the  ancient  shore  lines  thus 
approximated,  but  also  the  particular  oceanic  basins  from  which  the 
several  fossil  faunas  have  migrated  must  be  ascertained.  The  waters 
which  have  repeatedly  flooded  the  continent  have  come  from  the  Arctic, 
Atlantic  and  Pacific  oceans  and  the  Gulf  of  Mexico,  and  each  brought  with 
it  such  samples  of  its  own  particular  life  as  were  available  and  suited  to 
existence  in  shallow  epicontinental  seas. 

Comparative  studies  of  the  fossil  faunas  have  shown  them  to  have  had 
a  considerable  sameness  in  composition  when  derived  from  the  same 
oceanic  source,  and  to  have  had  great  unlikeness  to  contemporaneous 
faunas  that  originated  in  other  oceanic  basins.  This  appears  to  indicate 
not  only  that  the  life  in  the  several  oceanic  basins  evolved  more  or  less 
independently,  but  also  that  each  maintained  in  recognizable  measure 
its  individual  characteristics.  These  distinctive  facies  were  perhaps  never 
less  and  may  often  have  been  greater  than  now.  At  any  rate  Ordovician 
faunas  of  Arctic  origin  are  at  least  as  distinct  from  approximately  con- 
temporaneous ones  of  Gulf  origin  as  the  life  of  the  Arctic  Ocean  to-day  is 
different  from  that  of  the  Gulf  of  Mexico.  Appreciating  these  distinc- 
tions paleontologists  are  succeeding  very  well  in  discriminating  the  faunas 


MARYLAND  GEOLOGICAL  SURVEY  47 

that  came  in  from  the  east  or  south  from  those  that  invaded  the  continent 
from  the  north  or  west. 

The  underlying  principles  of  the  science  of  paleogeography  and  the 
methods  employed  in  the  preparation  of  paleogeographic  maps  have  been 
discussed  in  detail  by  Ulrich.1  In  brief  the  study  of  first,  fossil  faunas 
and  floras,  and  second,  of  the  phenomena  expressed  under  the  general 
name  of  diastrophism,  afford  the  data  for  such  maps.  In  the  study  of  the 
ancient  life  forms,  conclusions  of  value  are  reached  first,  by  determining 
the  areal  distribution  of  certain  associations  of  species  of  land  and  water 
organisms,  and  second,  by  the  discovery  of  their  place  of  origin. 

The  second  method  of  study,  based  on  diastrophism  depends  upon  the 
idea  of  essentially  permanent  depressions  and  elevations  of  the  earth's 
surface.  According  to  this  view  the  surface  of  the  continent  can  be 
divided  into  (1)  positive  areas  that  have  been  rarely  if  ever  submerged, 
this  being  shown  by  the  distribution  of  the  sedimentary  rocks  around  them ; 
and  (2)  negative  areas  which  often  received  deposits  from  waters  of  one 
or  another  of  the  oceanic  basins  whenever  by  subsidence  they  were  brought 
below  sea  level.  A  paleogeographic  map  therefore  is  produced  by  plotting 
the  isolated  occurrences  of  a  definitely  identified  fossil  fauna  and  connect- 
ing them  with  the  ocean  of  their  origin  by  sea  ways  within  the  negative 
areas. 

From  the  study  of  the  criteria  of  paleogeography  it  becomes  apparent 
that  the  Paleozoic  epicontinental  seas  occupied  mostly  small,  shallow, 
often  disconnected,  basins,  communicating  with  the  nearest  oceanic  basin. 
In  general  they  must  have  been  much  like  Hudson  Bay,  which  may  be 
regarded  as  a  modern  representative  of  an  American  interior  continental 
sea.  Many  of  these  land  basins  were  filled  and  emptied  many  times, 
occasionally  receiving  their  water  from  the  Atlantic  and  at  other  times 
from  the  Arctic,  and  ofttimes  from  the  Gulf  of  Mexico.  Naturally,  with 
each  change  in  the  source  of  the  waters,  the  geographic  pattern  differs 
considerably,  and  at  times  fundamentally,  from  the  next  preceding.  In 

i  Bull.  Geol.  Soc.  Amer.,  vol.  xxii,  1911,  No.  3,  pp.  281-680,  5  pis.  and  Compte 
Rendu,  XII  session  du  Congres  geologique  international,  pp.  593-667. 


48        THE  CAMBRIAN  AND  OKDOVICIAX  DEPOSITS  OF  MARYLAND 


Ordovician. 

Canadian. 

r»5#&[S^]S^T5^^, 

Finely  laminated  pure  magnesian  limestone  with 
cauliflower  and  other  cherts  at  top.  440  feet. 

1        1        1 

_  ,   1    .   1    1  1 

1      1 

Massive  pure  dove,  gray,  and  magnesian  limestone 
containing  the  Turritoma  fauna  in  its  upper 
part.  575  feet. 

1           1          1 

3eekmantown 
limestone. 

1  1  '  1  '  1  ' 

1     sE    ,'o    3 

Blue  and  dove  limestone,  cherty  in  upper  part  and 
containing  the  horn-like  fossil  Ceratopea.  250 
feet. 

I       I       / 

/       1 

1  '  °!     '         ?' 
i              r            I 

Cherty  oolitic  limestone,  dove-colored,  pure  lime- 
stone and  dense  textured  pink  marbles.  Basal 
60  feet  contains  Cryptozoon  steeli  and  weathers 
into  yellow  platy  chert.  600  feet. 

1              ' 
/            /            1 

II            1        1 

is  &  »      e  ti)  !  f>  6'     »  <3 

"  '.~|~    '„    |     o     e    |    .  V 

^^^^^ 

Stonehenge  member.  The  upper  half  of  massive 
blue  to  gray,  limestone  with  contorted  siliceous 
laminations  interbedded  with  edgewise  conglom- 
erates and  oolite.  The  lower  half  gray,  pure 
limestone,  weathering  white.  500  feet. 

-^^i^^^iJ-f<yJi^-fJ!rJ/ 

1                    1 

1                    1 

1                   1 

C 

.n 

Middle  Cambrian  (Acadian).  Ozarkian. 

Conococheague 
limestone. 

3°*t~iri^ir~ 

M       '       d     k  bl       1'        t           1  '     1     h     d  d  h  •  th' 

^^^^c^S 

siliceous  contorted  laminae,  weathering  into 
sandy  shale  fragments.  Edgewise  conglomerate, 
oolite  and  chert  abundant  at  the  base.  1600 
feet. 

i-i  t    i-  tr^f-L 

S25E5HxH 

r*       r11"       ~T        r1       h1 

Elbrook  formation. 

Light-blue  and  gray  shaly  limestone,  weathering 
into  shale  fragments.  Massive  dolomitic  and 
siliceous  limestone  developed  in  the  middle  part 

and  dark-blue  massive  limestone  at  the  base. 
3000  feet. 

.'I.-.    .-I.-.:  :  /  •-•.-.  /.-. 

'•••!••     '    •  '  '  -I  

^^^-=^=^i—  ^ 

i           1 

Waynesboro 

Siliceous  gray  limestone  and  calcareous  sandstone 
at  base,  massive  limestone  and  marble  in  middle 

1    i'         i             ' 

formation. 

1  1  1  

portion  and  red  to  purple  siliceous  shale  at  top. 
Forms  low  ridges  suitable  for  fruit  culture. 
1000  feet. 

£^-^2^=^!^- 

Lower  Cambrian  (Waucoban). 

Tomstown 
limestone. 

i              i 
i       i      i 

White  to  pink  shaly  marble  weathering  to  vellow- 
ish  shale  fragments,  with  also  massive  dark-blue 
magnesian  limestone.  Upper  beds  weather  into 
blocky,  black-banded  chalcedonic  chert.  1000 
feet  +. 

i       i 

i       i       i 

Antietam 
sandstone. 

SSSSSs1 

Coarse-grained  white  to  bluish-gray  sandstone  and 
quartzite,  weathering  readily  to  sand.  Contain 
numerous  Scolithus.  800  feet. 

Harpers  shale. 

5^—gssr 

Bluish-gray  sandy  shales,  slate,  schist,  and  thin 
flaggy  sandstones.  1200  feet. 

^c^    ^r"~  — 

l^^S-^-SE^S^^E:. 

^==^^~^^ 

Weverton 
sandstone. 

i.*  ;.;:.'..'  «"i  :.'.'.';  :.•»•.•;: 

Massive,  white  and  purple,  coarse,  feldspathic  sand- 
stone and  quartzite,  forming  mountain  ridges. 
800  feet. 

Loudon  formation. 

=~         —  —  — 

Dark  slates,  shales,  sandstones,  and  marbles.  500 
feet. 

Pre- 

cam- 
brian. 

y^^fe^g^Tr^ 

f^lS^Tsktt 

^j^F^Ww^f 

Altered  rhyolitic  lava  and  basalt  flows. 

FlG.    1. — COLUMNAR   SECTION   OF   THE   CAMBRIAN,   OZARKIAN   AND   CANADIAN    STRATA 
OF  MARYLAND  AND  NEIGHBORING  STATES. 


MARYLAND  GEOLOGICAL  SURVEY 


40 


Silu- 
rian. 

Tuscarora 
sandstone. 

.•••/. 

Massive  white  quartz  sandstone  and  conglomerate. 

Ordovician. 

Cincinnatian. 

Juniata  formation. 

m  ..,  ,. 

Unfossiliferous,  soft,  red  sandstone  and  inter- 
bedded  red  shale.  400  feet. 

;:  .'.'.'.'.;'  .'.''.'.  •;  '.  '.  v.v 

'-  '—  :_L  .'^-^fJ—  ;  —  '^^*^=f=: 

Unfossiliferous  gray  sandstone,  probably  of  Upper 
Maysville  age.  (Oswego  sandstone.)  150  feet. 

—  .-,  v.^vt^T-::  ~."-:~-^rr^- 

Unfossiliferous  gray  sandstone  with  Orthorhyn- 
chula  linneyi  zone  at  top.  Lower  Maysville  in 
age.  300  feet. 

Martinsburg   shale. 

''.'.''.'.'.."^''.'Tr.'  ••-  ••j77^i4_ 

Yellow  shale  and  calcareous  sandstone  in  upper 
half  and  soft  greenish  to  yellow  shaly  sandstone 
and  shale  in  lower  part.  Fossils  of  Eden  age  at 
several  horizons.  1000  feet  +. 

g-^gS^sis 

Dark  gray  Unfossiliferous  shale  in  upper  half  and 

Mohawkian. 

black  carbonaceous  fissile  shale  in  lower  half. 
Probably  of  Trenton  and  Utica  age.  1100  feet  -K 

T 

Calcareous  dark  shale  with  Corynoides  fauna. 
Thin-bedded,  limestone  with  Sinuites  fauna. 

TJreencastle  bed.  Heavy  bedded  impure  limestone. 
(Not  developed  in  Maryland.)  0-200  feet. 

^3  —  ^  —  r  —  "—  r-  — 

i 

Christiania  bed.  Thin-bedded  calcareous  shales 
and  shaly  limestone.  0-270  feet. 

I          i 

Chambersburg 
limestone. 

Nidulites  bed.  Compact  dark  gray,  thick  and  thin- 
bedded  limestone.  200-300  feet. 

I 

_tl_^r_ 

j^E^^-T  ,!„-- 

^rW-T-^f-^-r-  ^r 

Echinospherites  bed.  Dark  blue,  argillaceous, 
cobbly  limestone.  40-50  feet. 

i         1 

Tetradium  cellulosum  bed.  Fine-grained  dove  and 
subgranular  limestone.  0-200  feet. 

1- 

Caryocystites  bed.  Coarsely  crystalline  to  sub- 
crystalline  limestone.  0-175  feet. 

;  i  /  ,' 

r    • 

Chazyan. 

-s^^v 

Massive  fine-grained  dove-colored  limestone.  300 
feet  +. 

1 

1            1           1 

1 

i            i           [ 

0     |o     cu        c^>    c=>    |     a     <=, 

Blue  to  gray  compact  granular  to  oolitic  limestone 
with  Maclurites  magnus  fauna.  Weathers  into 
black,  blocky  chert.  200  feet. 

Stones  River 

=7|<=,         ^    0   |   =   V      0 

^  ,  i  „  —  i  j-T^  i  '-^  — 

i               i 

Massive  dove  limestone  interbedded  with  magnesian 
layers.  Cauliflower  chert  or  silicified  edgewise 
conglomerates  present  at  base.  600  feet  -<-. 

i 

Cherty  top  of  Beekmantown  limestone. 

1 

^S__O)    &£^2—f^5^£3 
^oj^oj    C3, 

PlG.    2. — COLUMNAR   SECTION   OF  THE  ORDOVICIAN   ROCKS   OF   MARYLAND  AND   NEIGH- 
BORING  STATES. 


50        THE  CAMBRIAN  AND  ORDOVICIAN  DEPOSITS  OF  MARYLAND 

the  Appalachian  region  the  seas  were  often  contained  in  narrow  troughs 
which  connected  at  some  point  with  the  Atlantic,  although  occasionally 
these  troughs  communicated  at  both  ends  with  the  ocean. 

The  complete  changes  in  the  source  and  direction  of  the  faunal  in- 
vasions are  well  shown  in  some  of  the  maps  of  North  America  in  Early 
Paleozoic  time.  For  example  the  Gulf  invasion  of  Lower  Black  Eiver 
(Lowville)  time  is  superseded  by  an  incursion  from  the  Arctic  in  the 
Middle  Black  Eiver  (Decorah)  and  this  is  followed  by  one  which  seems  to 
have  come  in  from  the  west. 

STEATIGEAPHIC  AND  PALEONTOLOGIC  CHAEACTEEISTICS 

Throughout  the  Appalachian  provinces  the  Early  Paleozoic  strata  com- 
prised in  the  Cambrian  and  Ordovician  systems  may  be  conveniently 
arranged  into  three  great  phases  of  sedimentation — the  lowest  of  sand- 
stone, quartzite,  and  sandy  shales  of  Lower  Cambrian  age,  next  limestone 
deposits  extending  from  uppermost  Lower  Cambrian  to  the  lower  part  of 
Middle  Ordovician  times,  and  last  a  shale  phase  covering  the  remaining 
Middle  and  Upper  Ordovician.  In  Appalachian  Maryland  each  of  these 
three  phases  is  well  developed,  their  combined  thickness  reaching  16,000 
feet.  Of  this  total,  the  lower  division  comprises  over  3300  feet,  the  middle 
limestones  over  10,000  feet,  and  the  upper  shales  2400  feet.  These  thick- 
nesses vary  in  different  parts  of  the  Appalachians.  As  a  rule  they  arc 
greatly  diminished  to  the  north  of  Maryland  and  much  increased  in  the 
states  to  the  south.  Columnar  sections  of  the  Cambrian  and  Ordovician 
rocks  of  Maryland  and  neighboring  states  are  presented  on  pages  48  and 
49.  while  a  correlation  table  of  these  strata  is  given  on  page  51. 

These  three  quite  different  lithologic  divisions  outcrop  in  equally  dis- 
tinct geographic  areas.  The  siliceous  rocks  are  confined  to  the  Blue  Eidge 
province,  the  limestones  form  the  floor  of  the  Appalachian  Valley,  and  the 
shales,  although  sometimes  occurring  as  a  great  infold  or  syncline  in  the 
limestone  in  the  middle  of  the  Valley,  are  best  developed  in  the  eastern 
ranges  of  the  Allegheny  ridges. 


52        THE  CAMBRIAN  AND  ORDOVICIAN  DEPOSITS  OF  MARYLAND 

East  of  the  Blue  Eidge  province,  sandstone  metamorphosed  into  quartz- 
ites,  limestone  changed  into  marbles,  and  shales  into  slates  or  schists, 
outcrop  in  small  patches  at  numerous  points  on  the  Piedmont  Plateau. 
Although  fossil  evidence  regarding  the  age  of  these  latter  strata  is  in 
most  cases  wanting,  it  is  believed  that  they  represent  at  least  portions  of 
the  three  phases  of  deposition  farther  west.  Their  correlation,  however, 
cannot  be  confirmed  until  the  geologic  history  of  the  Piedmont  province 
has  been  studied  in  detail.  The  present  volume  is  therefore  devoted  more 
to  the  discussion  of  the  stratigraphy  and  paleontology  of  the  Cambrian 
and  Ordovician  rocks  of  the  Blue  Ridge  and  more  western  provinces, 
although  for  the  sake  of  completeness,  brief  notes  on  the  Piedmont  strata 
of  apparently  the  same  age  are  introduced  in  their  appropriate  places. 

CAMBRIAN  SILICEOUS  FORMATIONS 

Although  the  siliceous  Lower  Cambrian  rocks  outcrop  in  long  but 
interrupted  stretches  from  Vermont  to  Alabama,  they  differ  so  greatly 
in  character  and  sequence  from  place  to  place  that  none  of  the  formations, 
if  any  were  ever  so  extended,  are  unquestionably  recognizable  throughout 
the  whole  Appalachian  province.  A  few  widely  separated  areas  have  been 
studied  in  detail,  but,  on  account  of  difficulties  in  correlation,  differing 
sets  of  local  names  had  to  be  applied  to  the  formations  distinguished  in 
each.  The  excellent  exposure  in  the  gorge  of  the  Potomac  Eiver  where  it 
breaks  through  the  Blue  Ridge  early  attracted  the  attention  of  geologists 
to  the  Maryland-Virginia  section.  The  sequence  of  formations  here 
determined  and  named  has  been  traced  to  the  north  across  the  state  into 
Pennsylvania  and  proved  satisfactory,  and  is  generally  accepted  as  the 
standard  for  the  Lower  Cambrian  in  the  north  middle  Appalachian 
region.  These  formations  and  their  thicknesses  arranged  in  geologic 
order,  are  as  follows : 

Table  of  Maryland  Lower  Cambrian  Siliceous  Formations 

Feet 

Antietam  sandstone.    Coarse  grained  white  to  bluish  sandstone 800 

Harpers  shale.    Bluish  gray  sandy  slates  and  schist 1200 

Weverton  sandstone.    Massive  white  and  purple  sandstone  and  quartzite. .  800 
Loudon  formation.    Dark  slates,  sandstone,  shales  and  marbles 500 


MARYLAND  GEOLOGICAL  SURVEY  53 

THE  LOUDON  FORMATION 

The  oldest  sedimentary  Paleozoic  rocks  in  Maryland  are  argillaceous 
dark  slates,  sandy  shales,  blue  limestones,  white  marble,  gray  sandstone, 
and  quartz  conglomerate,  immediately  overlying  the  crystalline  rocks 
and  known  collectively  as  the  Loudon  formation,  named  from  Loudon 
County,  Virginia,  where  all  the  members  are  well  displayed.  Weathering 
of  the  unconformably  underlying  Catoctin  schist  gave  rise  to  a  great 
variety  of  sediments,  Avhich  accounts  for  the  diverse  strata  composing  the 
succeeding  formation.  A  fine  grained,  dark  slate  usually  makes  up  the 
greater  part  of  the  Loudon  formation,  but  almost  all  of  the  other  varieties 
of  sedimentary  rocks,  especially  coarse  and  fine  conglomerate,  shale,  and 
pure  limestone  are  locally  developed. 

The  formation  outcrops  in  Maryland  in  depressions  and  valleys  with 
lines  of  small  hills  and  ridges.  It  gives  rise  to  a  thin,  micaceous,  sandy 
soil  of  little  importance  agriculturally.  The  rocks  are  exposed  in  long 
narrow  belts  along  several  lines  of  outcrop,  namely,  the  east  side  of  Elk 
Ridge,  both  sides  of  South  Mountain  and  both  sides  of  Catoctin  Mountain. 
In  the  granite  and  schist  area  between  Catoctin  Mountain  and  South 
Mountain  a  few  narrow  synclines  made  up  of  the  coarser  deposits  of  the 
formation  are  also  found.  The  finer  and  thinner  strata  of  the  formation 
occur  only  in  the  mountain  areas  mentioned  above  where  the  Weverton 
quartzite  overlies  the  Loudon  formation.  The  limestone  occurs  as  lenses 
in  the  slate,  and  in  Maryland  has  been  found  only  along  a  line  just  west 
of  Catoctin  Mountain  for  a  distance  of  a  mile  or  two  north  of  the  Potomac 
River.  This  limestone  is  usually  metamorphosed  into  marble,  but  the 
marbles  are  interbedded  with  slate  and  schist  and  are  almost  always  too 
poorly  developed  to  be  worked  for  commercial  purposes.  However,  almost 
every  outcrop  of  this  limestone  has  in  the  past  afforded  rock  for  lime. 

The  black  slate  makes  up  a  large  part  of  the  Loudon  formation  in 
Maryland,  especially  along  the  Catoctin  Mountain  line  of  outcrop.  Here 
the  thickness  is  not  over  200  feet,  but  along  the  Blue  Ridge  at  Turner's 
Gap,  10  miles  north  of  the  Potomac  River,  a  thickness  of  500  feet  has 
been  measured.  All  trace  of  the  original  bedding  in  these  slates  has  been 


54        THE  CAMBRIAN  AND  ORDOVICIAN  DEPOSITS  OF  MARYLAND 

lost  by  metamorphism  during  the  folding  of  the  rocks.  The  Loudon  slate 
can  be  f  ouncl  at  localities  one  mile  east  of  Harper's  Ferry  and  half  a  mile 
south  of  Rohrersville,  Maryland,  with  coarse  fragments  of  the  Catoctin 
schist  such  as  epidote  and  jasper  imbedded  in  it. 

The  conglomerates  of  the  Loudon  formation,  with  few  exceptions,  are 
confined  to  the  synclinal  areas  where  the  Weverton  sandstone  is  not 
present.  These  conglomerates  are  limited  in  extent  and  are  composed  of 
quartz,  granite,  jasper,  and  epidote  boulders  imbedded  in  the  usual  black 
slate.  Grains  of  magnetite  and  ilmenite  washed  from  the  Catoctin  schist 
are  present  in  many  of  the  beds.  Sandstones  likewise  occur,  but  these  are 
thin  and  unimportant  in  Maryland,  their  greatest  development  being 
south  of  the  Potomac  River. 

The  Loudon  formation  as  a  whole  has  been  subjected  to  much  meta- 
morphism and  its  various  members  exhibit  the  usual  metamorphic  prod- 
ucts, namely,  quartzite,  slate,  schist,  and  marble.  The  alteration  is  most 
marked  in  the  argillaceous  beds  where  all  trace  of  their  original  stratifica- 
tion has  been  lost  in  the  change  to  slate  and  schist.  This  slate  and  the 
few  marble  areas  weather  readily,  forming  low  ground.  The  more 
siliceous  rocks,  metamorphosed  into  quartzite,  resist  weathering  and  as  a 
result  form  the  low  hills  or  ridges  of  the  Loudon  areas. 

No  fossils  have  been  discovered  in  the  Loudon  formation,  the  conditions 
of  sedimentation  being  unfavorable  for  the  preservation  of  organic  re- 
mains. These  rocks,  however,  apparently  mark  the  beginning  of  the 
siliceous  Lower  Cambrian  deposits,  the  age  of  which  is  determined  by 
paleontological  evidence  in  the  overlying  Harpers  shale  and  Antietam 
sandstone. 

THE  WEVERTON   SANDSTONE 

The  prominent  outcrops  in  the  gorge  of  the  Potomac  River  at  the  south 
end  of  South  Mountain  near  Weverton,  Maryland,  consist  of  massive  beds 
of  fine,  pure,  white  and  purple  sandstone,  quartzite,  and  conglomerate, 
overlying  the  basal  Cambrian  Loudon  formation.  These  strata,  termed 
the  Weverton  sandstone,  are  the  most  resistant  of  all  the  Cambrian  and 
Ordovician  deposits,  and  for  that  reason  they  are  the  main  mountain- 


56        THE  CAMBRIAN  AND  ORDOVICIAN  DEPOSITS  OF  MARYLAND 

making  formation  of  the  Blue  Eidge  province.  Elk  Eidge,  South  Moun- 
tain, and  Catoctin  Mountain  are  the  principal  elevations  in  Maryland 
due  to  the  resistant  Weverton  sandstone  and  it  is  along  their  crests  that 
the  formation  is  exposed.  Sugar  Loaf  Mountain  is  the  easternmost  eleva- 
tion due  to  this  formation. 

This  sandstone  is  composed  almost  entirely  of  siliceous  fragments, 
mainly  quartz  and  feldspar,  firmly  cemented  together  and  often  changed 
into  quartzite.  The  color  of  the  finer  sandstone  is  white,  and  the  coarser 
gray  to  purple.  Streaks  of  bluish  black  and  black  sometimes  occur  in  the 
white  sandstone  on  South  Mountain.  Feldspathic  material  is  present  in 
greatest  abundance  at  the  northern  end  of  Catoctin  Mountain,  but  its 
occurrence  does  not  change  the  general  aspect  of  the  formation.  As  a 
rule,  however,  the  Weverton  is  usually  composed  of  well-worn  quartz 
grains  washed  clear  of  argillaceous  material.  Cross  bedding  is  not  an 
uncommon  occurrence. 

As  the  quartz  particles  forming  the  main  mass  of  the  Weverton  sand- 
stones do  not  admit  of  much  alteration,  this  formation  has  been  subjected 
to  comparatively  little  metamorphism,  even  when  it  has  been  greatly 
folded.  Slight  schistosity  has  been  noted  in  the  southern  part  of  Catoctin 
Mountain,  but  the  development  of  quartzite  is  the  usual  occurrence. 

The  Weverton  sandstone  varies  little  in  composition  from  place  to  place, 
but  the  thickness  is  subject  to  much  variation.  Along  Elk  Ridge  its  thick- 
ness is  about  500  feet.  At  the  type  locality  near  Weverton,  the  thickness 
is  also  about  500  feet,  but  northward  along  South  Mountain  this  increases 
to  800  feet.  A  similar  increase  in  thickness  is  seen  in  the  Catoctin 
Mountain  area. 

This  formation  is  not  only  of  no  value  agriculturally,  but  the  debris 
from  it  lessens  the  value  of  neighboring  areas.  It  decays  very  slowly  into 
quartz  sand  and  its  heavy  blocks  cover  the  mountain  sides  and  the  con- 
tiguous lowlands.  The  mountain  streams  carry  great  quantities  of 
boulders  of  Weverton  sandstone  out  on  the  surrounding  areas  where  they 
are  deposited  as  a  drift  formation  not  unlike  glacial  deposits.  South 
Mountain  has  furnished  boulders  of  white  quartzite  and  sandstone,  which 


MARYLAND  GEOLOGICAL  SURVEY 


CAMBRIAN  AND  ORDOVICIAN,  PLATE  III 


FlG.   I. — VIEW  OF  THJE  GREAT  VALLEY   FROM    SOUTH   MOUNTAIN  AT  BLUE  MOUNTAIN   STATION. 


FlG.   2. — VIEW   ALONG  ROAD  BETWEEN   PEN    MAR  AND   HIGH   ROCK,    MARYLAND,    SHOWING 
MOUNTAIN   SIDE  COVERED  WITH   BLOCKS   OF  WEVERTON   QUARTZITE. 


57 

are  now  spread  out  in  all  the  lowland  areas  of  the  Hagerstown  Valley  in  a 
strip  one  to  two  miles  wide  paralleling  the  mountain. 

Fossils  have  not  been  found  in  this  sandstone,  but  as  it  is  a  part  of  the 
siliceous  series  terminated  by  the  Antietam  sandstone,  which  contains 
a  Lower  Cambrian  fauna,  the  age  of  the  Weverton  sandstone  also  is  very 
probably  Lower  Cambrian. 

THE    HARPEKS    SHALE 

The  bluish  gray  slate  or  schist  exposed  so  prominently  in  the  vicinity 
of  Harper's  Ferry,  West  Virginia,  in  the  gorges  of  the  Potomac  and 
Shenandoah  rivers  and  known  as  the  Harpers  shale,  follows  the  Weverton 
sandstone  in  the  geological  column,  although  its  outcrops  are  almost 
everywhere  included  between  faults.  In  southern  Maryland  the  Harpers 
shale  is  composed  almost  entirely  of  sandy  slates  with  a  few  sandstone 
layers  developed  in  its  upper  portion.  These  shales  are  of  a  dull  bluish- 
gray  color  when  freshly  exposed,  but  they  weather  to  a  light  greenish- 
gray.  Northward  in  Maryland  the  sandstone  layers  increase  in  thickness 
until,  in  the  region  of  Pen  Mar,  and  especially  at  Montalto  Mountain  in 
southern  Pennsylvania,  a  massive  quartzite  750  feet  in  thickness  is 
developed  in  the  middle  portion  of  the  schist.  This  is  the  Montalto 
quartzite  member  mapped  by  Stose  in  the  Chambersburg  (Pennsylvania) 
quadrangle,  but  it  is  hardly  of  sufficient  importance  in  Maryland  to  be 
distinguished  as  a  separate  unit.  This  Montalto  member  is  only  20  feet 
thick  just  north  of  the  Maryland  line,  but  it  thickens  to  850  feet  going 
northward  a  distance  of  20  miles  in  Pennsylvania. 

As  no  complete  section  of  the  Harpers  shale  is  exposed  in  Maryland 
or  even  in  its  other  areas  of  outcrop,  its  thickness  is  difficult  to  determine. 
Moreover  one  or  often  both  sides  of  its  areas  of  outcrop  are  cut  off  from 
adjoining  formations  by  faults.  At  Harper's  Ferry,  the  type  area  of 
outcrop,  the  thickness  has  been  estimated  by  Keith  as  1200  feet.  .  In 
southern  Pennsylvania  northeast  of  Waynesboro  the  thickness  is  increased 
to  2750  feet,  due  in  part  to  the  development  of  the  Montalto  quartzite 
member. 


58        THE  CAMBRIAN  AND  ORDOVICIAN  DEPOSITS  OF  MARYLAND 

The  typical  outcrop  of  the .  Harpers  shale  extends  northward  from 
Harper's  Ferry  into  Maryland  for  several  miles  in  a  belt  a  mile  or  less 
in  width,  following  the  western  slope  of  Elk  Ridge  until  it  is  terminated 
by  a  fault  against  the  Tomstown  limestone,  a  mile  south  of  Keedysville. 
A  second  belt  of  outcrop  is  one-half  mile  wide  and  follows  the  western 
slope  of  South  Mountain  across  the  state.  The  last  and  easternmost  belt 
occurs  on  the  eastern  side  of  Catoctin  Mountain. 

The  decay  of  the  Harpers  shale  gives  rise  to  soils  of  moderate  value 
when  its  areas  of  outcrop  are  not  too  deeply  covered  with  sandstone  debris 
from  the  adjacent  mountain  sandstone  ridges.  As  an  example  of  the 
latter  feature,  the  entire  area  of  outcrop  of  this  shale  west  of  South 
Mountain  in  Maryland  is  covered  with  a  thick  deposit  of  such  sandstone 
boulders.  So  far  as  known  the  only  clean  exposures  of  the  shale  itself 
are  in  cuts  of  the  Western  Maryland  Railway  in  its  ascent  of  South 
Mountain  to  Pen  Mar,  and  in  certain  road  and  stream  cuttings. 

With  the  exception  of  casts  of  the  worm  burrow  Scolithus  lineans  no 
fossils  have  been  found  in  the  Harpers  shale.  Its  age,  however,  is  un- 
doubtedly Lower  Cambrian  because  it  forms  a  part  of  the  same  series  of 
siliceous  sediments  as  the  overlying  Antietam  sandstone  which  contains 
typical  Lower  Cambrian  fossils. 

THE  ANTIETAM  SANDSTONE 

The  Harpers  shale  forming  the  western  slope  and  foot  hills  of  South 
Mountain  is  found  to  contain  an  infolded  sandstone  formation  wherever 
a  conspicuous  elevation  is  developed  in  front  of  the  main  ridge.  Such 
front  ridges  of  South  Mountain  owe  their  origin  to  coarse  grained  white 
to  bluish-gray  quartzite  and  sandstone  about  500  feet  in  thickness,  which 
weathers  readily  to  a  white  sand.  This  is  the  Antietam  sandstone,  so 
named  from  the  good  exposures  on  the  tributaries  of  Antietam  Creek 
east  of  Sharpsburg,  Maryland.  This  sandstone  is  .the  uppermost  of  the 
mountain-making  formations  of  the  Blue  Ridge  province  and  is  the  last 
of  the  siliceous  deposits  of  Lower  Cambrian  age.  It  is  composed  of  small 
grains  of  white  quartz,  «vorn  and  assorted,  cemented  together  by  a  small 


MARYLAND  GEOLOGICAL  SURVEY  f>9 

percentage  of  carbonate  of  lime.  Its  color  is  usually  white,  but  some  of 
the  upper  layers  change  to  a  dull  brown.  Actual  outcrops  of  the  rock  are 
very  rare,  but  its  presence  can  be  determined  readily  by  the  numerous 
lumps  of  white  sandstone  strewing  the  surface  and  by  its  topographic 
form.  On  account  of  their  location  and  the  abundance  of  rock  fragments 
in  the  soil,  its  areas  of  outcrop  are  unsuitable  for  agriculture  other  than 
the  growth  of  fruit  trees. 

The  Antietam  sandstone  does  not  outcrop  in  a  continuous  belt  like  the 
associated  formations,  but  is  displayed  in  a  number  of  small  areas  just 
west  of  the  main  elevation  of  South  Mountain.  Its  occurrence  coincides 
with  that  of  the  Harpers  shale,  and  indeed  Keith's  detailed  mapping  has 
shown  that  this  sandstone  is  found  only  as  synclinal  remnants  lying  upon 
the  shale.  The  largest  of  these  areas  in  Maryland  are  the  ridge  about 
four  miles  long  just  east  of  Ponds ville  and  the  V-shaped  ridge  east  of 
Mapleville.  The  elevation  just  east  of  Boonsboro  likewise  is  composed 
of  Antietam  sandstone,  while  a  few  small  areas  are  infolded  in  the 
Harpers  shale  belt  just  north  of  Eohrersville.  The  western  foot  hills  of 
Elk  Ridge  likewise  contain  a  few  small,  scattered  areas,  while  the  larger 
elevation  two  miles  east  of  Sharpsburg  is  composed  almost  entirely  of 
this  formation.  The  Harpers  shale  belt  on  the  east  side  of  Catoctin 
Mountain  contains  small,  schistose,  sandy  beds  lying  above  the  Harpers 
shale  which  may  be  the  metamorphosed  equivalent  of  the  Antietam  sand- 
stone. 

Except  a  few  worm  burrows  in  the  sandstone  member  of  the  Harpers 
shale,  the  Lower  Cambrian  deposits  in  Maryland  are  practically  un- 
fossiliferous  beneath  the  upper  part  of  the  Antietam  sandstone.  Even 
here  fossils  are  by  no  means  common  at  any  place.  In  Maryland  the  best 
locality  for  fossils  is  in  the  sandstones  along  the  mountain  front  near 
Eakles  Mills  where  fragments  of  Olenellus  thompsoni  Hall,  Hyolithes 
communis  Billings,  and  Obolella  minor  Walcott  have  been  found  by  Wal- 
cott.  These  fossils  are  associated  with  the  Scolithus  tubes  which  are 
abundant  in  the  upper  part  of  the  formation  at  practically  all  of  its  out- 
crops. This  fauna,  although  small,  is  sufficient  to  determine  the  age  of 


60        THE  CAMBRIAN  AND  ORDOVICIAN  DEPOSITS  OF  MARYLAND 

the  Antietam  sandstone  as  Lower  Cambrian.  The  same  association  of 
species  has  been  found  on  Observatory  Hill,  two  miles  south  of  Keedys- 
ville  and  at  a  locality  about  one  mile  southeast  of  Smithsburg. 

CAMBRIAN-ORDOVICIAN  LIMESTONES 

The  second  great  phase  of  deposition  in  the  Appalachian  region  com- 
prises a  group  of  limestones  which,  from  the  fact  that  these  strata  form 
the  floor  of  the  great  Valley,  were  first  named  the  Valley  limestone.  In 
Virginia,  the  geographical  term  Shenandoah  limestone  was  subsequently 
substituted  for  Valley  limestone  of  the  older  geologists.  In  all  the  earlier 
maps  of  the  central  Appalachian  Valley  this  limestone  was  regarded  as  a 
single  formation  and  its  thickness  was  supposed  to  approximate  5000  feet. 
This  calcareous  phase  of  deposition  between  the  Cambrian  siliceous  rocks 
and  the  Ordovician  shales  is  such  a  conspicuous  feature  throughout  the 
Appalachian  Valley  that  various  local  names  have  been  applied  to  it.  In 
Maryland  the  name  Shenandoah  formation  was  used  for  this  limestone 
until  comparatively  recent  years  when  geologic  work  in  adjacent  areas 
of  Pennsylvania  showed  that  these  strata  can  be  subdivided  into  seven 
distinct  formations  with  an  aggregate  thickness  of  over  10,000  feet.  The 
names,  age,  and  thickness  of  these  seven  formations  are  as  follows : 

Table  of  Cambrian-Ordovician  Limestones  in  Maryland 

Feet 

Middle  Ordovician,  Chambersburg  limestone 300 

Lower  Ordovician,  Stones  River  limestone 1000 

Lower  Ordovician  ( Canadian  )-Beekmantown  limestone  (Stonehenge  mem- 
ber at  base) 2500 

Upper  Cambrian  (Ozarkian)-Conococheague  limestone 1600 

Middle  Cambrian. .  fElbrook  formation 3000 

\  Waynesboro  formation 1000 

Lower  Cambrian-Tomstown  limestone 1000 

All  of  the  above  formations  may  be  more  or  less  readily  recognized  by 
lithologic  peculiarities,  by  the  contained  fossils,  by  the  topographic  forms 
and  residual  debris  which  their  weathering  produces  and  by  their  known 
position  in  the  stratigraphic  sequence.  Limestones  of  similar  aspect  may 
be  found  common  to  all  the  formations,  but  fortunately  the  boundary 


MARYLAND  GEOLOGICAL  SURVEY  61 

between  adjoining  divisions  commonly  is  marked  by  one  or  more  dis- 
tinctive lithologic  features  which  aid  considerably  in  the  delimitation 
of  the  formations. 

THE  TOMSTOWN  LIMESTONE 

The  lowest  division  of  the  "  Shenandoah  "  is  a  thick  limestone  forma- 
tion which  outcrops  along  the  eastern  edge  of  the  Appalachian  Valley 
just  west  of  the  Blue  Ridge  or  the  equivalent  mountain  range  in  a 
narrow  strip  often  largely  covered  by  sandstone  debris  from  the  adjacent 
mountain.  These  rocks  are  usually  highly  tilted  and  as  a  result  the 
band  of  outcrop  is  often  quite  narrow.  In  Virginia  this  limestone 
received  the  designation,  Sherwood  limestone,  and  more  recently  the 
corresponding  beds  in  southern  Pennsylvania  were  termed  the  Toms- 
town  limestone  on  account  of  their  outcrop  at  Tomstown,  Franklin 
County.  In  Maryland  the  area  of  outcrop  of  the  Tomstown  limestone  is 
broader  than  usual  because  these  strata  are  here  not  so  sharply  folded. 

TOPOGRAPHY. — The  Tomstown  limestone  is  the  most  soluble  of  all  the 
formations  outcropping  in  the  eastern  part  of  the  Appalachian  Valley. 
Its  outcrops  therefore  occur  only  in  lowland  areas.  As  the  overlying 
formation,  the  Waynesboro,  is  composed  in  large  part  of  sandstone  and 
shale,  it  resists  weathering  and  solution  much  more  than  the  Tomstown 
limestone  and  forms  hills  in  contrast  to  the  limestone  valley  between  them 
and  South  Mountain.  Within  this  valley,  however,  there  are  long,  narrow 
elevations  trending  northeast-southwest  which  owe  their  origin  to  syn- 
clinal infolding  of  remnants  of  Waynesboro  sandstone.  Some  of  the  pro- 
nounced hills  of  this  valley  region,  however  are  underlain  by  limestone, 
but  these  elevations  also  have  resulted  from  differential  resistance  to 
weathering,  as  they  are  formed  in  large  part  of  black  banded  chert  which 
is  a  characteristic  component  of  the  upper  beds  of  the  Tomstown.  A 
good  example  of  a  Tomstown  limestone  valley  is  the  lowland  area  in  which 
Cavetown  is  located  with  a  ridge  of  the  Waynesboro  formation  to  the  west 
and  the  foothills  of  Harpers  shale  and  South  Mountain  of  Weverton  sand- 
stone on  the  east. 


62        THE  CAMBRIAN  AND  ORDOVICIAN  DEPOSITS  OF  MARYLAND 

Exposures  of  this  limestone  are  infrequent  because  its  area  of  outcrop, 
lying  as  it  does  at  the  foot  of  South  Mountain,  commonly  is  covered  by  a 
thick  deposit  of  mountain  wash  in  addition  to  its  own  mantle  of  soil. 
This  mountain  wash  is  thickest  and  most  widely  spread  where  streams 
from  the  mountain  enter  the  valley  and  form  alluvial  cones.  In  Mary- 
land, however,  as  mentioned  above,  this  Lower  Cambrian  limestone  is 
often  only  moderately  folded  and  this,  in  connection  with  other  factors, 
causes  its  area  of  outcrop  to  be  much  wider  than  in  neighboring  states. 
Overturned  folds  and  faults  are  not  uncommon,  but  as  a  rule  these  are  of 
relatively  insignificant  proportions  so  that  the  usual  condition  of  gently 
dipping  strata  is  soon  resumed.  Such  a  fold  with  slight  faulting  is  well 
displayed  along  the  Western  Maryland  Railway,  one  mile  west  of 
Cavetown. 

LITHOLOGIC  CHARACTERS. — In  the  type  area,  southern  Pennsylvania, 
the  Tomstown  limestone  is  described  as  a  formation  Composed  largely  of 
thin  bedded  and  massive  dolomite  and  limestone  with  considerable  shale 
interbedded  near  the  base.  The  rocks  are  not  well  exposed  in  Pennsyl- 
vania and  it  is  possible  that  the  marbles  which  are  such  a  conspicuous 
feature  of  the  formation  in  Maryland  are  present  also  in  Pennsylvania. 
At  any  rate  proceeding  southward  into  Maryland  the  main  mass  of  the 
formation  consists  of  white  to  pinkish  shaly  marble  which  upon  weather- 
ing gives  rise  to  yellow  and  greenish  shale-like  fragments  quite  sericitic 
in  nature.  The  Tomstown  limestone  is  especially  well  exposed  in  a  belt 
of  outcrop  three  miles  in  width  southeast  of  Hagerstown,  where  the  usual 
drift  deposits  are  not  so  thick  and  widely  dispersed.  In  this  area  ex- 
posures, particularly  of  the  middle  and  upper  beds  of  the  formation,  are 
numerous. 

The  lowest  beds  of  the  Tomstown  are  not  well  exposed  in  Maryland, 
being  nearly  everywhere  buried  beneath  the  mountain  wash.  However, 
it  is  believed  that  the  gray  to  dark  blue  massive,  rather  pure  limestone 
exposed  in  the  large  quarry  at  Cavetown  represents  some  portion  of  the 
lower  Tomstown,  since  at  this  point  the  Tomstown  is  faulted  against  the 
Waynesboro  and  the  characteristic  marbles  are  not  in  evidence.  The 


MARYLAND  GEOLOGICAL  SURVEY 


CAMBRIAN  AND  ORDOVICIAN,  PLATE  IV 


FlG.  I. — EXPOSURE  OF  TOMSTOWN  LIMESTONE  ALONG  TROLLEY  LINE  JUST  SOUTHEAST  OF 
WAGNERS  CROSS  ROAD,  WASHINGTON  COUNTY,  MARYLAND,  ILLUSTRATING  WEATHERING  OF 
MASSIVE  SHEARED  LIMESTONE  INTO  SHALE  FRAGMENTS. 


FlG.   2. — LIMESTONE   QUARRY   AT  CAVETOWN,    MARYLAND,    SHOWING   TOMSTOWN   LIMESTONE 
FAULTED  AGAINST  WAYNESBORO  SANDSTONE. 


MARYLAND  GEOLOGICAL  SURVEY  63 

uppermost  beds  of  the  formation,  on  the  contrary,  are  very  commonly 
exposed  in  Maryland  because  there  are  so  many  small  areas  of  the  over- 
lying Waynesboro  formation  yet  remaining  in  the  valley  to  mark  the  top 
of  the  Tomstown.  These  upper  strata,  while  still  retaining  pinkish  to 
pearl-colored  marble  beds,  also  comprise  massive  dark  blue  magnesian 
limestones.  Most  of  the  limestones  of  the  Tomstown,  and  especially  the 
marbles,  exhibit  some  lamination  with  the  result  that  upon  weathering  the 
rock  is  easily  split  into  thin  slate-like  fragments.  This  lamination  is 
usually  quite  regular,  but  in  southern  Maryland  there  is  a  body  of  Toms- 
town  limestone  where  the  rock  is  so  irregularly  laminated  that  it  weathers 
into  a  mottled  effect.  Shearing  of  this  laminated  limestone  is  frequent, 
especially  in  the  marbles.  Such  strata  give  the  characteristic  fracture  due 
to  the  combination  of  lamination  and  shearing. 

The  shape  of  the  characteristic  shale  fragments  resulting  from  the 
weathering  of  this  limestone  is  due  to  this  same  combination  of  lamination 
and  shearing,  so  that,  while  many  of  the  pieces  are  broken,  others  are 
undulated  or  twisted.  The  shearing  planes  are  marked  on  the  residual 
shale-like  fragments  by  thin  films  of  silky,  sericite-like  material.  Some- 
what similar  shale  fragments  result  from  the  weathering  of  the  Elbrook 
formation.  When  the  Tomstown  and  Elbrook  limestones  are  brought  in 
contact  by  f aulting-out  of  the  intervening  Waynesboro  formation,  careful 
discrimination  is  necessary  to  identify  the  formations  correctly.  In 
doubtful  cases  it  is  necessary  to  search  for  an  outcrop  of  the  rock  furnish- 
ing the  shale  residue.  When  this  has  been  found  it  should  be  easy  to 
distinguish  the  sheared  marbles  of  the  Tomstown  from  the  dull  laminated 
clayey  limestone  of  the  Elbrook. 

RESIDUAL  PRODUCTS. — One  of  the  characteristic  residual  products  of 
the  Tomstown  is  black  banded  chert  in  small  blocky  pieces  left  in  the  soil 
upon  the  weathering  of  the  upper  beds  of  the  formation.  This  chert  is 
almost  chalcedonic  in  nature  and  the  black  bands  passing  through  it  give 
it  somewhat  the  aspect  of  agate.  Chert  of  this  particular  nature  is  not 
found  again  until  the  middle  division  of  the  Stones  Eiver  limestone,  and 
as  there  is  little  danger  of  confusing  these  two  widely  separated  forma- 


64        THE  CAMBRIAN  AND  ORDOVICIAN  DEPOSITS  OF  MARYLAND 

tions  which  are  also  quite  distinct  lithologically,  the  banded  chalcedonic 
chert  of  the  Tomstown  can  be  relied  upon  as  a  distinguishing  feature  as 
much  as  a  characteristic  fossil.  The  usual  fragment  of  this  chert  is  a 
block  four  or  five  inches  long,  several  inches  wide  and  an  inch  or  two 
thick.  The  upper  and  lower  surfaces  are  uneven  and  coarsely  pitted,  but 
the  interior  is  of  dense  black  and  lighter  colored  silica  almost  waxy  enough 
to  be  called  chalcedony.  This  chert  in  the  soil  is  largely  responsible  for 
the  maintenance  of  those  hills  in  the  Tomstown  limestone  valley  which  are 
not  capped  by  the  Waynesboro  formation.  The  hills  southwest  of 
Pondsville  are  due  to  the  chert  of  the  upper  Tomstown. 

A  second  residual  product  of  the  Tomstown  limestone  is  the  yellow  to 
greenish  shale  fragments  resulting  from  the  weathering  of  the  marbles 
of  the  formation.  As  the  black  chert  occurs  only  in  the  upper  part  of  the 
Tomstown  and  the  shaly  marbles  occur  throughout  its  thickness,  these 
shale  fragments  are  more  widely  dispersed  than  the  chert  and  therefore 
may  be  said  to  be  more  characteristic  of  the  formation  as  a  whole.  The 
decay  of  the  shaly  marbles  into  yellow  and  greenish  shales  is  well  dis- 
played in  the  cut  of  the  Hagerstown-Frederick  trolley  road  just  east  of 
Wagner's  Cross  Roads.  At  the  bottom  of  the  cut  the  rocks  are  massive 
limestones,  although  much  sheared.  Near  the  top,  solution  has  removed 
much  of  the  lime  and  the  strata  are  easily  broken  into  shaly  blocks.  At 
the  surface  itself  the  separation  into  shale  fragments  is  complete,  each 
fragment  being  covered  with  a  soapstone-like  film,  in  many  cases  not 
unlike  sericite. 

ECONOMIC  FEATURES. — The  decomposition  of  the  Tomstown  limestone 
results  in  a  firm,  compact  soil,  but  over  most  of  the  area  this  soil  has  been 
lightened  and  made  more  porous  by  admixture  with  the  sand  and  gravel 
from  the  nearby  mountains.  This  is  particularly  true  on  the  lower  slopes 
of  South  Mountain  where  the  orchards  of  the  famous  South  Mountain 
peach  belt  are  to  a  great  extent  located  on  such  well-drained  soil. 

In  the  past,  kilns  for  the  burning  of  agricultural  lime  were  numerous 
in  the  Tomstown  area,  but  this  practice  has  now  been  discontinued.  At 
present  the  only  quarry  of  consequence  where  the  Tomstown  limestone  is 


MARYLAND  GEOLOGICAL  SURVEY 


FlG.  I. — VALLEY  OF  TOMSTOWN  LIMESTONE  LOOKING  EAST  FROM  CAVETOWN,  MARYLAND, 
SHOWING  FOOTHILLS  OF  HARPERS  SHALE,  AND  SOUTH  MOUNTAIN  OF  WEVERTON  SANDSTONE 
IN  THE  DISTANCE. 


FlG.  2. — VALLEY  OF  TOMSTOWN  LIMESTONE  WITH  SOUTH  MOUNTAIN  IN  THE  DISTANCE 
SHOWING  PENEPLAINED  SURFACE.  THE  HILL  JUST  BEYOND  THE  HOUSE  IS  CAPPED  BY 
TOMSTOWN  CHERT.  PHOTOGRAPH  TAKEN  ONE  MILE  SOUTH  OF  CAVETOWN,  MARYLAND. 


MARYLAND  GEOLOGICAL  SURVEY  -65 

utilized  for  lime  and  ballast  is  at  Cavetown,  where  good  location  and 
transportation  facilities  are  at  hand. 

The  marbles  of  the  Tomstown  were  formerly  quarried  to  a  considerable 
extent,  especially  in  the  southern  part  of  the  area,  but  at  present  the  only 
development  is  near  Eakles  Mills.  White  marbles  which  occur  at  several 
horizons  in  the  formation,  have  been  most  frequently  quarried.  With 
these  is  a  bed  of  a  cream-white  color  with  a  very  fine  texture,  but  the 
associated  beds  are  impure  and  have  the  more  usual  grayish  banded 
appearance.  The  pinkish  shaly  marbles  likewise  include  some  pure  white 
beds  which  might  be  profitably  quarried  if  transportation  facilities  were 
available.  An  abandoned  quarry,  situated  on  the  bank  of  Beaver  Creek, 
one  mile  northeast  of  Harmony  Hill  school,  gives  a  good  exposure  of  these 
light  colored  marbles. 

AREAL  DISTRIBUTION. — The  outcrops  of  the  Tomstown  limestone  are 
confined  to  the  eastern  part  of  the  Hagerstown  Valley  just  west  of  the 
Blue  Eidge  in  a  belt  of  low  land  at  the  foot  of  South  Mountain  about  two 
miles  wide  in  the  northernmost  portion,  increasing  to  a  width  of  three 
miles  or  more  southward.  Along  the  entire  eastern  border  of  the  forma- 
tion the  Harpers  shale  is  faulted  against  this  limestone  with  the  inter- 
vening formation,  the  Antietam  sandstone,  either  wanting  or  outcropping 
some  little  distance  east  of  the  Tomstown  as  an  infold  in  the  shale.  The 
western  border  of  the  Tomstown  limestone  in  northern  Maryland  as  far 
south  as  the  Western  Maryland  Eailway  is  the  normally  overlying 
Waynesboro  formation.  South  of  this,  the  Tomstown  is  faulted  first 
against  the  Elbrook  formation,  then  against  the  Conococheague  limestone 
as  at  Chewsville,  then  against  the  Elbrook  again  for  some  miles,  and 
finally  at  Benevola  on  the  National  pike,  the  succession  becomes  normal 
again.  A  fault  passing  north  and  south  just  east  of  Boonsboro  parallels 
South  Mountain  and  along  its  western  side  several  small  areas  of  Waynes- 
boro are  exposed.  West  of  this  fault  in  the  middle  of  the  Tomstown 
valley  the  line  of  hills  starting  a  mile  north  of  Smithsburg  and  ending 
near  Beaver  Creek  are  formed  by  an  infolded  area  of  the  Waynesboro 
formation.  With  these  exceptions  and  several  small  areas  where  the 


G6        THE  CAMBRIAN  AND  ORDOVICIAN  DEPOSITS  or  MARYLAND 

Waynesboro  formation  is  nothing  but  a  surface  remnant,  all  the  valley 
east  of  the  line  first  mentioned  is  composed  of  the  Tomstown  limestone. 

THICKNESS.— In  spite  of  numerous  good  exposures,  no  continuous  sec- 
tions of  any  thickness  of  the  Tomstown  limestone  are  exposed  in  Mary- 
land, and  indeed  no  place  has  been  found  where  the  normal  sequence  can 
be  determined.  In  southern  Pennsylvania  an  approximate  thickness  of 
1000  feet  has  been  measured.  This  has  been  accepted  as  the  thickness  in 
Maryland,  although  in  the  southern  half  of  the  state  where  the  marbles 
are  well  developed  a  greater  thickness  is  possible. 

AGE  AND  CORRELATION. — No  fossils  have  so  far  been  noted  in  the 
Tomstown  limestone  in  Maryland  and  indeed  the  sheared  marbles  and 
dolomitic  strata  of  the  formation  are  not  favorable  for  the  occurrence  of 
organic  remains.  In  southern  Pennsylvania  near  Roadside  and  near 
Waynesboro,  fragments  of  the  mollusk  shell  Salterella  have  been  collected. 
A  few  miles  north  of  this  at  the  foot  of  the  mountain  east  of  Little 
Antietam  Creek  fragments  of  the  characteristic  Lower  Cambrian  trilobite 
Olenellus  were  discovered  by  Walcott.  A  Lower  Cambrian  age  for  the 
formation  is  therefore  accepted,  although  the  paleontological  evidence  is 
still  quite  meager.  Fossil  evidence  in  the  rocks  holding  the  same  strati- 
graphic  position  in  states  to  the  south  is  also  very  slight,  but  favors  the 
same  age.  The  most  interesting  of  these  fossils  is  a  large  species  of 
Archeocyathus  recently  found  in  the  Sherwood  limestone  and  a  similar 
large  species  of  the  same  genus  in  the  Shady  limestone. 

In  contrast  with  the  few  fossils  of  the  areas  just  mentioned  is  the 
abundant,  well-preserved  Lower  Cambrian  fauna  found  in  limestones 
and  shales  in  the  vicinity  of  York  and  Fruitville,  Pennsylvania.  It  seems 
probable  that  these  f ossilif erous  strata  form  a  part  of  the  Tomstown 
limestone,  but  the  lithology  is  so  different  that  a  close  study  of  the  inter- 
vening area  is  necessary  before  this  correlation  can  be  made  with 
certainty. 

THE    WAYNESBORO    FORMATION 

Viewed  as  a  lithologic  unit  the  most  obvious  and  easily  recognized 
formation  in  the  Shenandoah  limestone  series  is  the  mass  of  reddish  to 
purple  calcareous  sandstone  and  shale  here  known  as  the  Waynesboro 


MARYLAND  GEOLOGICAL  SURVEY 


CAMBRIAN  AND  ORDOVICIAN,  PLATE  VI 


FlG.     I.— OVERTURNED    FOLD    WITH    SLIGHT    FAULTING    IN    TOMSTOWN    LIMESTONE 
ALONG  WESTERN  MARYLAND  RAILWAY,  ONE  MILE  WEST  OF  CAVETOWN,  MARYLAND. 


FlG.  2. — RIDGE  OF  THE  WAYNESBORO  FORMATION  JUST  EAST  OF  MIDDLE  BRIDGE,  ANTIETAM 
BATTLEFIELD,  WASHINGTON  COUNTY,  MARYLAND. 


67 

formation.  These  striking  beds  form  more  or  less  conspicuous  ranges  of 
hills  in  the  lowland  area  just  west  of  the  Blue  Ridge  and  corresponding 
mountain  ranges  to  the  north  and  south  of  Maryland.  Weathering  of 
these  red  to  purple  strata  results  in  similarly  colored  soils  which  there- 
fore contrast  strongly  with  the  grayish-brown  and  black  soils  of  adjacent 
limestone  areas. 

NAME  AND  SYNONYMY. — In  publications  upon  the  central  and  northern 
part  of  the  Appalachian  Valley  the  red  zone  mentioned  above  was  fre- 
quently noted,  especially  in  folios  of  the  United  States  Geological  Survey, 
but  it  was  not  separated  as  a  distinct  formation  until  1905  *  when 
H.  D.  Campbell  proposed  the  name  Buena  Vista  shale  for  corresponding 
red  beds  in  central  western  Virginia.  Later  Stose 2  discriminated  similar 
sandstones  and  shales  in  southern  Pennsylvania  as  the  Waynesboro  forma- 
tion, the  typical  development  of  which  extends  southwestward  from 
Waynesboro,  Pennsylvania,  into  Maryland,  where  its  outcrops  form  the 
"  peach  lands  "  in  the  valley  west  of  the  Blue  Eidge  slope.  The  formation 
here  being  the  same  in  general  character  and  sequence  of  beds  as  in 
Pennsylvania  it  is  manifestly  desirable  to  use  the  same  name  for  it  in  both 
states.  It  is  not  yet  finally  decided  whether  this  name  should  be  the  one 
proposed  by  Stose  or  some  other.  Regarding  the  term,  Buena  Vista,  it 
cannot  be  used  in  this  connection  because  the  same  name  had  been  given 
many  years  before  to  rocks  in  Ohio.  Among  several  probably  synonymous 
terms  that  have  been  considered,  the  name  Wautaga  shale,  proposed  in 
1903  by  Keith,3  for  series  of  red  and  green  shales'  in  east  Tennessee,  occu- 
pying apparently  the  same  stratigraphic  position  as  the  Maryland  forma- 
tion under  consideration,  is  perhaps  the  most  appropriate  designation. 
According  to  Keith  the  Wautaga  shale  has  been  traced  far  enough  north- 
ward to  warrant  the  application  of  this  rame  in  west  central  Virginia  in 
place  of  the  preoccupied  term  Buena  Vista;  and  there  may  be  sufficient 
reason  for  its  extension  to  Maryland  and  southern  Pennsylvania.  How- 
ever, the  lithologic  development  of  this  northern  f  acies  of  the  Appalachian 

1Amer.  Jour.  Sci.,  vol.  xx,  1905,  pp.  445-447. 

2  Folio  170,  U.  S.  Geol.  Surv.,  1910. 

3  Cranberry  folio,  No.  90,  U.  S.  Geological  Survey,  1903. 


68        THE  CAMBRIAN  AND  ORDOVICIAN  DEPOSITS  OF  MARYLAND 

Middle  Cambrian  red  beds  for  which  the  term  Waynesboro  was  proposed, 
is  different  from  the  Wautaga  facies  to  the  south  in  that  considerable 
thicknesses  of  sandstone  and  limestone  are  intercalated  with  the  char- 
acteristic-red and  purple  shales.  Moreover,  there  are  two  other  names 
whose  claims  must  be  considered  before  this  nomenclatural  question  can 
be  finally  settled.  These  names  are  the  Eome  sandstone  and  shale  and 
Eussell  shale,  both  in  good  standing  and  of  prior  dates  than  Wautaga 
shale.  Provisionally,  therefore,  it  is  thought  advisable  to  retain  the  name 
Waynesboro  formation  for  these  strata  in  Maryland  and  Pennsylvania. 

LITHOLOGIC  CHARACTER  AND  THICKNESS. — In  Maryland  as  well  as  in 
the  type  area  of  outcrop,  the  Waynesboro  formation  consists  of  a  lower 
member  of  very  siliceous  gray  limestone  and  calcareous  sandstone,  a 
middle  member  of  limestone,  and  an  upper  one  of  red  and  purple  siliceous 
shale,  aggregating  1000  feet  in  thickness.  Of  the  three  members,  the 
upper  is  the  best  developed  and  most  frequently  exposed,  since  faulting 
often  cuts  out  the  middle  limestone  and  lower  sandstone  divisions.  The 
weathering  of  this  upper  part  is  mainly  responsible  for  the  characteristic- 
red  color  of  the  soils  derived  from  the  formation.  The  basal  siliceous 
limestones  weather  into  shaly,  porous  sandstone  with  which  are  associated 
numerous  blocks  of  secondary  white  vein  quartz  and  rounded  corrugated 
sandy  fragments  full  of  crevices  lined  with  small  quartz  crystals.  The 
limestones  of  the  middle  division  range  from  dark  blue  massive  limestone 
to  fine  grained  white  marble  which,  on  account  of  their  soluble  nature, 
are  generally  not  exposed.  In  Pennsylvania  this  middle  portion  is  several 
hundred  feet  thick,  but  in  Maryland  the  thickness  is  probably  not  as 
great.  These  limestones  become  siliceous  toward  the  top  of  the  member 
and  finally  seem  to  grade  into  the  dark  red  to  purple  sandy  shale  which 
makes  the  upper  part  of  the  formation.  Certain  parts  of  the  upper  mem- 
ber contain  argillaceous  flaggy  sandstone  which  has  been  locally  quarried 
for  paving  stones.  On  weathered  surfaces  the  flags  break  up  into  frag- 
ments of  sandy  shale. 

Such  slabs  frequently  exhibit  ripple  marks  and  mud  cracks,  the  latter 
being  well  displayed  in  some  of  the  paving  stones  of  Smithsburg.  One 


MARYLAND  GEOLOGICAL  SURVEY 


CAMBRIAN  AND  GflDOVJtJIAN, 


IRON-STAINED  CONTORTED  SANDSTONE  OF  WAYNESBORO  FORMATION.  THE  UPPER  FIGURE 
REPRESENTS  THE  USUAL  ASPECT  OF  THE  ROCK.  THE  CAVITIES  IN  THE  SANDSTONE  ARE  COVERED 
BY  DRUSY  QUARTZ  AS  SHOWN  IN  THE  FIGURE  TO  THE  LEFT  (X  2)  OR  BY  BEAUTIFUL  MINUTE 
CRYSTALS  OF  QUARTZ  ILLUSTRATED  IN  FIGURE  TO  RIGHT  (X  6). 


MARYLAND  GEOLOGICAL  SURVEY  69 

of  these  showed  the  interesting  occurrence  of  two  sets  of  intersecting  mud 
cracks,  one  set  about  a  foot  apart  and  the  other  about  four  inches. 

TOPOGRAPHIC  FORM. — Faulting  is  so  frequent  along  the  eastern  edge 
of  the  Waynesboro  outcrops  in  Maryland  that  the  normal  sequence  of 
strata  is  seldom  apparent.  Siliceous  strata  always  form  a  part  of  the 
Waynesboro  wherever  developed,  so  that  its  topographic  form  is  always  an 
elevated  area.  If  the  strata  have  been  strongly  folded  this  highland  area 
assumes  the  form  of  elongated  hills  paralleling  South  Mountain.  Should 
the  normal  sequence  of  the  three  divisions  of  the  Waynesboro  occur,  the 
basal  siliceous  strata  will  give  rise  to  a  range  of  low  hills  nearest  the 
mountain  and  the  upper  sandy  shales  will  occasion  another  range  to  the 
west,  the  narrow  depression  between  them  being  underlain  by  the  less 
resistant  limestones  of  the  middle  portion. 

TOMSTOWN-WAYNESBORO  BOUNDARY. — The  base  of  the  Waynesboro 
formation  is  formed  of  a  very  siliceous  gray  limestone  which  weathers  to 
slabby,  porous  sandstone.  Except  in  very  fresh  exposures  the  limestone 
nature  of  this  part  of  the  formation  is  not  apparent  and  it  seems  to  be 
made  up  of  sandstone  entirely.  Sandstone  slabs  are  very  abundant  on  the 
weathered  slopes  and  associated  with  them  are  large  masses  of  contorted, 
minutely  laminated,  iron  stained,  sandy  rocks,  with  numerous  cavities 
filled  with  beautiful  drusy  quartz.  These  masses  are  sometimes  several 
feet  in  diameter  and  their  presence  in  the  fields  and  especially  in  the 
fences  identifies  this  basal  portion  of  the  Waynesboro.  Wherever  in 
Maryland  the  Waynesboro  sequence  is  normal  such  iron  stained,  drusy 
quartz  masses  are  found  in  abundance.  Associated  with  this  sandy  rock 
and  also  in  the  higher  strata  of  the  lower  portion  of  the  Waynesboro  are 
numerous  fragments  of  secondary  white  vein  quartz  which  in  connection 
with  the  other  siliceous  rock  helps  in  identifying  the  basal  beds.  Plate 
VII  represents  a  small  fragment  of  the  contorted  sandy  masses  in 
which  all  the  crevices  are  filled  with  minute  quartz  crystals.  An  enlarged 
view  of  a  drusy  quartz  portion  of  one  of  these  masses  is  shown  on  the 
same  plate.  The  crystals,  though  perfectly  formed,  are  so  small  as  to  be 
indistinguishable  without  a  magnifying  lens.  To  the  unaided  eye  the 


70        THE  CAMBRIAN  AND  ORDOVICIAN  DEPOSITS  OF  MARYLAND 

surface  of  this  drusy  quartz  has  a  beautiful  velvety  appearance,  the  beauty 
of  which  is  enhanced  by  the  lemon-yellow  to  brownish-olive  color  with  just 
enough  reflection  from  the  minute  crystals  to  add  a  silvery  sheen  to  the 
surface.  Other  specimens  of  the  same  rock  show  these  crystals  increased 
to  a  length  of  about  2  mm.  and  a  magnified  view  exhibits  their  perfection 
of  form.  These  crystals  are  interesting  in  that  practically  all  of  those 
observed  are  terminated  by  a  single  rhombohedron  instead  of  the  two 
usually  found  in  quartz. 

AREAL  DISTRIBUTION. — The  geologic  structure  of  the  various  occur- 
rences of  the  Waynesboro  formation  in  Maryland  varies  considerably.  The 
normal  section  from  upper  Tomstown  through  the  Waynesboro  into  the 
overlying  Elbrook  is  present  only  in  the  strip  of  outcrops  extending  from 
Benevola  southwest  to  Burnside  Bridge  east  of  Sharpsburg,  and  even 
here  both  ends  of  the  strip  are  faulted.  The  ridge  east  of  the  Upper 
Bridge  and  Middle  Bridge  of  the  Antietam  battle-field  exposes  the 
different  divisions  of  the  formation  to  best  advantage  for  study.  Here 
only  does  the  limestone  middle  portion  form  its  characteristic  topographic 
feature  of  a  valley  between  the  two  ridges  left  by  the  lower  and  upper 
siliceous  parts.  Northeast  of  Benevola  is  a  number  of  small  outcrops 
which  in  most  cases  are  little  more  than  surface  remnants.  The  same 
holds  true  of  several  lines  of  outcrop  east  of  Chewsville  where  the  rocks 
are  of  such  little  depth  that  the  underlying  limestone  is  occasionally 
plowed  up  in  the  fields.  A  shallow  syncline  commences  one  and  a  half 
miles  north  of  Smithsburg  and  terminates  seven  miles  to  the  southwest 
near  Beaver  Creek,  one  mile  northeast  of  Wagner's  Cross  Eoads,  in  another 
normal  syncline.  These  two  syncline  terminal  areas  are  connected  by  a 
narrow  strip  of  the  formation  in  which  the  greater  part  of  its  thickness 
is  covered  by  overthrust  faulting.  Thus  in  the  limestone  quarry  at  Cave- 
town  the  lower  part  of  the  Tomstown  limestone  is  faulted  against  the 
purple  shales  of  the  Waynesboro.  An  interesting  anticline  of  Waynesboro 
sandstone  exposing  the  upper  Tomstown  with  its  characteristic  black 
banded  chalcedonic  chert  in  its  axial  part,  enters  the  state  from  Pennsyl- 
vania and  is  terminated  by  faulting  at  Ringgold. 


MARYLAND  GEOLOGICAL  SURVEY  71 

On  the  western  edge  of  the  Valley  the  Waynesboro  outcrops  in  a  narrow 
strip  along  the  eastern  base  of  Fairview  and  Powell  mountains,  where  it 
is  brought  to  the  surface  by  faulting.  Few  outcrops  can  be  found  in  this 
area,  however,  since  the  country  is  so  thoroughly  covered  with  drift 
material  from  the  nearby  mountains. 

ECONOMIC  FEATURES. — Compared  with  the  neighboring  limestone 
areas  the  soils  derived  from  the  weathering  of  the  Waynesboro  formation 
are  comparatively  poor  and  the  fields  are  frequently  covered  with  small 
sandstone  or  sandy  purple  shale  slabs  and  milky  quartz  fragments. 
Freshly  plowed  fields,  especially  when  wet,  have  a  distinct  purple  to  red 
color.  As  the  formation  always  outcrops  topographically  above  the 
adjoining  areas,  and  as  the  soil  is  quite  porous,  Waynesboro  areas  have 
both  good  water  and  air  drainage.  This  causes  such  areas  to  be  of 
especial  value  for  fruit  culture,  and  as  a  result  most  of  the  Waynesboro 
hills  have  been  cleared  and  planted  in  orchards,  peaches  being  the  fruit 
most  commonly  raised. 

From  a  commercial  standpoint  the  Waynesboro  formation  is  of  little 
importance.  When  there  was  a  strong  local  demand  for  iron  .years  ago, 
it  afforded  small  quantities  of  residual  iron  ore.  The  limestones  in  the 
middle  portion  have  in  the  past  been  employed  very  locally  for  lime  burn- 
ing. The  thin-bedded  sandstones  make  excellent  flagging  stones  which 
are  used  in  the  villages  close  to  the  areas  of  outcrop.  Mention  of  the 
suncracked  flagstones  in  the  pavements  of  Smithsburg  has  been  made 
in  a  preceding  paragraph. 

AGE  AND  CORRELATION. — No  fossils  have  been  observed  in  the  Waynes- 
boro formation  in  Maryland,  but  at  the  type  locality  just  north  of  the 
Maryland  line  a  few  poorly  preserved  phosphatic  brachiopods  of  the 
genus  Lingulella  have  been  noted.  These  suggest  a  Middle  Cambrian 
age.  The  Buena  Vista  shale  of  Virginia  has  yielded  an  Olenellus-likQ 
trilobite  which  would  suggest  a  Lower  Cambrian  age  for  this  shale, 
although  in  recent  years  the  range  of  Olenellus  has  been  extended  into 
the  Middle  Cambrian.  The  age  of  the  Waynesboro  is  therefore  not  clearly 
indicated  by  paleontologic  evidence,  but  stratigraphic  and  diastrophic 
data  place  it  as  Middle  Cambrian. 


72        THE  CAMBRIAN  AXD  ORDOVICIAX  DEPOSITS  OF  MARYLAND 

THE  ELBROOK  FORMATION 

Overlying  the  purple  shales  of  the  Waynesboro  formation  in  the  normal 
section  is  a  thick  series  of  light-blue  and  gray  shaly  limestone  and 
calcareous  shales  which,  in  Maryland,  are  seldom  exposed  in  natural 
outcrops.  These  strata  were  not  recognized  as  a  distinct  formation  until 
1910,  when  Stose1  named  them  the  Elbrook  formation  from  the  village 
on  the  Western  Maryland  Railway  in  southern  Pennsylvania. 

LITHOLOGIC  CHARACTER  AND  THICKNESS. — The  shaly  limestone  and 
calcareous  shale  making  up  the  major  portion  of  the  Elbrook  formation 
weathers  very  rapidly  into  shale  fragments,  so  that  usually  there  are  few 
natural  outcrops.  In  stream  valleys  and  artificial  exposures  the  following 
general  succession  has  been  determined.  At  the  very  base  of  the  formation 
are  beds  of  rather  pure  dark  blue  massive  limestones  not  over  100  feet 
thick  which  have  afforded  the  only  fossils  found.  Succeeding  this  and 
constituting  approximately  the  lower  third  of  the  formation  is  1000  or 
more  feet  of  minutely  laminated  shaly  limestone  and  calcareous  yellow 
to  green  and  some  reddish  shale  which  weathers  into  calcareous  shaly 
plates.  The  middle  of  the  formation  is  marked  by  siliceous  limestones 
and  massive  beds  of  dolomite  which  form  a  slight  elevation  in  the  gen- 
erally low  area  of  outcrop  of  the  formation.  The  upper  half  of  the 
formation  is  composed  of  light  colored  calcareous  shale  and  impure 
laminated  limestones  which,  like  the  lower  part,  weather  shaly.  How- 
ever, it  is  slightly  more  siliceous  than  the  lower  third  and  weathers  into 
more  irregular  often  cubical  sandy  red  to  brownish  fragments.  It  is 
followed  by  the  limestone  conglomerates  and  sandy  oolite  marking  the 
base  of  the  succeeding  Conococheague  limestone.  The  total  thickness  of 
the  Elbrook  as  determined  in  both  northern  and  southern  Maryland  is 
about  3000  feet. 

AREAL  DISTRIBUTION. — Notwithstanding  its  great  thickness  the 
Elbrook  formation  occupies  less  area  in  Maryland  than  almost  any  other 
of  the  Cambrian  or  Ordovician  formations.  It  appears  at  the  surface  in  a 
narrow  northeast-southwest  band  crossing  the  state  in  the  .eastern  part 

1  Folio  170,  U.  S.  Geol.  Surv. 


MARYLAND  GEOLOGICAL  SURVEY 


CAMBRIAN  AND  ORDOVICIAN,  PLATE  VIII 


FIG.  i. — EXPOSURE  OF  ELBROOK  LIMESTONE  ALONG  BALTIMORE  AND  OHIO  RAILROAD  JUST 

SOUTH    OF     SHARMAN,     MARYLAND.       THESE     MASSIVE    BEDS     WEATHER    INTO    THIN     SHALY 
LAYERS. 


FlG.  2. — VIEW  LOOKING  NORTH  OVER  ANTIETAM  BATTLEFIELD  SHOWING  EXPOSURE  OF 
ELBROOK  LIMESTONE.  PHOTOGRAPH  TAKEN  ONE-HALF  MILE  EAST  OF  SHARPSBURG,  ALONG 
ROAD  TO  BURNSIDE  BRIDGE,  MARYLAND. 


MARYLAND  GEOLOGICAL  SURVEY  73 

of  the  Hagerstown  Valley  and  in  a  still  narrower  band  along  the  extreme 
western  edge  of  the  Great  Valley.  The  eastern  area  of  outcrop  enters 
the  state  from  Pennsylvania  just  north  of  Ringgold  and  proceeding  south- 
ward in  a  strip  less  than  a  mile  in  width  is  terminated  by  a  fault  near 
Qhewsville.  South  of  Chewsville  the  throw  of  this  fault  becomes  less,  so 
that  the  Elbrook  formation  reappears  at  the  surface  and  continues  south- 
ward in  a  band  averaging  a  mile  in  width  paralleling  the  hills  of  the 
Waynesboro  formation  on  the  east.  At  Sharpsburg  beyond  the  extremity 
of  an  infolded  mass  of  the  overlying  limestone,  the  Elbrook  is  partly 
repeated  in  the  two  limbs  of  the  syncline  and  the  outcrop  correspondingly 
widened. 

The  western  band  of  outcrop  doubtless  parallels  North  Mountain,  hut 
is  known  only  from  a  few  exposures,  as  almost  its  entire  area  is  covered 
by  mountain  wash.  The  beds  dip  steeply  in  these  exposures,  so  that  the 
outcrop  of  the  formation  must  be  confined  to  a  strip  scarcely  exceeding 
a  half  mile  in  width. 

TOPOGRAPHIC  FORM  AND  RESIDUAL  PRODUCTS. — Where  the  geologic 
section  is  normally  developed,  two  ranges  of  pronounced  hills — those  of 
the  siliceous  Waynesboro  on  the  east,  those  of  the  siliceous  limestones  of 
the  Conococheague  on  the  west — flank  a  lowland  in  which  the  less 
resistant  limestones  and  shales  of  the  Elbrook  are  at  the  surface.  However, 
this  lowland  band  is  not  a  simple  valley,  but  is  divided  longitudinally 
into  two  narrow  valleys  by  a  series  of  low  hills  due  to  the  relatively 
resistant  beds  of  siliceous  limestone  and  dolomite  that  occur  in  the  middle 
part  of  the  Elbrook. 

The  topographic  form  of  the  Elbrook  is  not  unlike  that  of  the  Toms- 
town  and  the  shale  fragments  left  in  the  soil  from  both  formations  arc 
quite  similar.  In  areas  where  the  intervening  Waynesboro  formation  is 
cut  out  by  faulting,  such  as  the  area  about  five  miles  southeast  of  Hagers- 
town, great  care  must  be  exercised  in  discriminating  the  two  formations. 
Determined  search  in  areas  of  Tomstown  limestone  will  sooner  or  later 
reveal  outcrops  of  the  characteristic  sheared  marble  which  on  weathering 
leave  the  shale-like  residual  fragments.  On  the  other  hand,  in  an  Elbrook 


74        THE  CAMBRIAN  AND  ORDOVICIAN  DEPOSITS  OF  MARYLAND 

area  the  simulating  residual  shale  will  be  traced  to  merely  dull  laminated 
limestone  or  calcareous  shale. 

A  characteristic  weathering  product  of  the  lower  half  of  the  Elbrook  is 
light  colored,  sometimes  almost  white,  waxy  translucent  chert  approach- 
ing chalcedony  in  appearance  and  structure.  This  appears  in  the  soil  in 
small  fragments,  usually  only  a  few  inches  thick  with  more  or  less  rounded 
edges.  The  color  of  this  chert  is  sometimes  a  light  yellow  or  even  light 
red,  but  it  is  never  black  nor  banded  like  the  Tomstown  chalcedonic  chert. 

AGE  AND  CORRELATION. — Fossils  have  been  found  only  in  the  basal 
limestones  of  the  formation  in  the  vicinity  of  Waynesboro,  Pennsylvania. 
These  consist  mainly  of  well-preserved  heads  and  tails  of  two  species  of 
trilobites,  one  of  which,  a  species  of  Dolichometopus,  is  not  uncommon. 
These  trilobites  belong  to  new  species  whose  age  relations  have  not  been 
definitely  determined.  However,  as  they  are  closely  allied  to  species 
known  to  be  characteristic  Middle  Cambrian  fossils  it  seems  highly  prob- 
able that  the  Elbrook  is  of  similar  age. 

THE   CONOCOCHEAGUE  LIMESTONE 

On  the  northwest,  north  and  east  flanks  of  the  Adirondack  uplift  the 
Potsdam  sandstone  grades  upward  through  passage  beds  into  a  limestone 
to  which  Ulrich  and  Gushing  have  applied  the  name  Hoyt  limestone. 
This  is  succeeded  by  a  massive  dolomite  known  as  the  Little  Falls  dolo- 
mite. Fossils  have  been  found  in  all  three  of  these  formations,  but  are 
reasonably  plentiful  only  in  the  Hoyt  limestone.  The  fauna  of  this 
limestone  was  first  procured  and  in  part  briefly  described  by  Walcott 
many  years  ago.  Recently  the  same  authority  revised  and  completed  his 
studies  of  the  Hoyt  and  Potsdam  faunas,  the  results  being  published  in  a 
small  monograph.  As  now  known  these  early  New  York  "  Saratogan  " 
faunules  comprise,  besides  a  number  of  trilobites  and  shells  of  various 
kinds,  large  concentrically  laminated  masses  in  reef -like  aggregations. 
These  masses  are  thought  to  be  calcareous  algae.  Two  species  are  dis- 
tinguished, one  having  been  described  by  Hall  under  the  name  Cryptozoon 
proliferumj  the  other  is  a  related  new  species.  These  two  species  have 


76        THE  CAMBRIAN  AND  OEDOVICIAN  DEPOSITS  OF  MARYLAND 

an  important  bearing  on  the  age  determination  of  certain  formations  in 
the  Appalachian  Valley.  Apparently  the  same  species  occur  abundantly 
in  the  basal  part  of  the  Kittatinny  limestone  in  the  Lehigh  Valley  of 
Pennsylvania  and  nearby  areas  in  New  Jersey  where  they  are  associated 
with  trilobites  of  the  same  general  types  as  those  found  near  Saratoga, 
New  York. 

In  the  Cumberland  Valley  of  southern  Pennsylvania  these  same  species 
of  Cryptozoon  are  found  in  the  basal  part  of  a,  thick  series  of  siliceous 
banded  limestone  that  lies  between  the  Middle  Cambrian  Elbrook  lime- 
stone and  another  great  mass  of  relatively  pure  limestone  that  corresponds 
to  the  well-known  Beekmantown  limestone  of  the  New  York  section. 
This  intervening  formation  which  is  about  to  be  described  was  dis- 
tinguished and  mapped  by  Stose  in  the  Mercersbutrg-Chambersburg 
(Pennsylvania)  folio  of  the  U.  S.  Geological  Survey  as  the  Conococheague 
limestone,  so  called  from  the  good  exposures  along  the  banks  of  Conoco- 
cheague Creek  near  Scotland,  Pennsylvania.  From  this  place  the  forma- 
tion extends  in  typical  development  to  the  Great  Valley  of  Western  Mary- 
land, where  its  outcrops  cover  a  considerable  area. 

LITHOLOGIC  CHARACTERS. — The  main  body  of  the  Conococheague  lime- 
stone is  composed  essentially  of  massive  dark-blue,  closely  banded  lime- 
stones. The  banding  is  usually  one-half  to  one  inch  in  width  and  is 
caused  by  the  alternation  of  thin,  wavy,  sandy  laminae  with  thin  layers 
of  purer  rock.  The  sandy  laminae  are  inconspicuous  in  the  freshly 
fractured  rock,  although  close  examination  reveals  the  alternation  of 
the  dark  blue  purer  and  gray  siliceous  limestone  bands  quite  clearly. 
Upon  weathering,  the  siliceous  laminae  appear  as  yellowish  sandy 
streaks  separating  light-blue  or  gray  bands  of  limestone.  Further 
weathering  causes  the  siliceous  laminae  to  stand  out  in  relief  as  more  or 
less  parallel  ribs.  Finally,  where  the  rock  has  suffered  complete  disin- 
tegration, these  laminae  are  left  in  the  soil  as  hard,  siliceous  thin  plates. 
Strata  of  this  nature  can  be  found  in  almost  any  outcrop  of  the  formation, 
but  interbedded  with  them  are  various  other  types  of  limestone.  Of  these, 
the  most  striking  are  the  beds  of  "  edgewise  "  conglomerate  which  alter- 
nate frequently  with  the  usual  banded  limestone.  This  conglomerate  is 


MARYLAND  GEOLOGICAL  SURVEY 


FlG.  I. — CRYPTOZOON  REEF  AT  BASE  OF  CONOCOCHEAGUE  FORMATION,  EXPOSED  ALONG 
NORFOLK  AND  WESTERN  RAILROAD  ABOUT  ONE  MILE  SOUTHWEST  OF  ANTIETAM  STA- 
TION, MARYLAND,  PHOTOGRAPH  ABOUT  ONE-FIFTEENTH  NATURAL  SIZE. 


FlG.  2.— CRYPTOZOON  STRUCTURE  IN  UPPER  PART  OF  CONOCOCHEAGUE  LIMESTONE  EXPOSED 
ALONG  WESTERN  MARYLAND  RAILWAY,  ONE-FOURTH  MILE  WEST  OF  CHARLTON  MARYLAND 
PHOTOGRAPH  ONE-SIXTH  NATURAL  SIZE.  THE  OOLITES  HAVE  BEEN  OUTLINED  IN' INK 


MARYLAND  GEOLOGICAL  SURVEY  77 

composed  of  slender  fragments  of  limestone  tilted  at  all  angles  in  a 
matrix  of  limestone  distinctly  different  in  composition. 

The  general  nature  of  the  strata  composing  the  Conococheague  lime- 
stone is  shown  in  the  type  section  near  Scotland,  Pennsylvania,  published 
by  Stose.  The  continuity  of  this  section  is  known  to  be  interrupted  by 
small  faults  and  folds.  Although  allowances  were  made  for  these,  the 
section,  as  finally  compiled,  is  scarcely  to  be  considered  as  entirely  satis- 
factory. The  total  thickness  may  be  greater  than  given. 

Section  of  Conococheague  Limestone  West  of  Scotland,  Pennsylvania 

Feet 

Rather  pure  light-colored  limestone,  much  sheared,  followed  above  by 
siliceous  banded   dark   limestone  and   "  edgewise "   conglomerate 
(Stonehenge  member  of  Beekmantown). 
Granular  limestone  with  coarse  "  edgewise  "  conglomerate,  oolite,  and 

fine-grained  pink  marble,  with  numerous  slaty  partings 90 

Covered    .- . . .     300 

Pure  dove-colored  even-grained  limestone  interbedded  with  light 
siliceous-grained  cross-bedded  limestone,  coarse  "  edgewise "  con- 
glomerate, and  chert 15 

Largly  covered :  dark  impure  limestone  with  large  banded  chert  at  the 

base 390 

Dark  and  light  limestone,  in  part  banded  with  impurities 10 

Dark,  rather  impure  limestone  with  argillaceous  partings  weathering 
to  slaty  fragments  and  soft  yellow  shale;  contains  trilobites  and 

beds  of  oolite  180 

Dark  limestone  with  shaly  partings  on  weathering 90 

Massive  beds  of  light,  dense,  even-grained  limestone  with  few  wavy 

siliceous  partings  weathering  in  relief 40 

Covered    70 

Wavy  impure  siliceous  banded  limestone,  weathering  hackly  and  shaly.     180 

Dense  black  impure  limestone,  weathering  with  thick  gray  coating 30 

Thick  massive  beds  of  crumpled  siliceous  banded  limestone 40 

Section  folded  and  discontinuous.  Dense  siliceous  banded  limestone, 
with  sandy  beds,  oolite,  "  edgewise  "  conglomerate,  and  layers  of 
Cryptozoon  at  the  base ' 200± 


1635± 

The  exposures  of  the  Conococheague  limestone  in  Maryland  are  too 
discontinuous  to  allow  a  complete  section  to  be  taken  at  any  particular 
locality.  The  following  general  section  gives  the  sequence  of  these  rocks 
east  of  the  Martinsburg  shale  belt  of  the  Valley. 


78        THE  CAMBRIAN  AND  ORDOVICIAN  DEPOSITS  OF  MARYLAND 

General  Section  of  the  Conococheague  Limestone  in  the  Hagerstown 
Valley,  Maryland 

Feet 

Massive,  rather  pure,  light  colored  limestone  with  cephalopoda  and  gastro- 
pods of  the  Stonehenge  limestone. 

Pink  marbles,  oolite,  granular  limestone  with  edgewise  conglomerate  and 
massive  fine  grained  light  colored  limestone  separated  by  beds  of 
banded  dark  blue  siliceous  limestone.  Vein  quartz  with  crystals  and 
yellow  chert  are  left  in  soil  upon  weathering 400 

Dark  impure  banded  limestone  weathering  to  slaty  fragments  and  banded 

chert.    Occasional  beds  of  edgewise  conglomerate 600 

Wavy,  blue  to  black  siliceous  banded  impure  limestone  with  layers  of 

edgewise  conglomerate   400 

Siliceous  banded  dark  blue  limestone  with  intercalcated  sandy  beds,  oolite 
and  edgewise  conglomerate.  On  weathering  some  of  the  strata  give 

rise  to  large  chunks  of  scoriaceous  chert 200 

'Massive  dark  blue  to  light  colored  rather  pure  limestone  with  reefs  of 

Cryptozoon  proliferum  Hall  and  C.  undulatum  new  species 50 

Light  colored  calcareous  shale  and  laminated  impure  limestone  of  the 
Elbrook  formation,  weathering  shaly. 


Total  1650 

Because  of  the  discontinuous  exposure  of  the  formation  and  the  folding 
to  which  it  has  been  subjected  the  thickness  is  a  difficult  matter  to  deter- 
mine. The  above  total  of  1650  feet  is  apparently  a  fair  average  for 
Maryland. 

Although  five  divisions  are  shown  above  in  the  general  section  of  the 
Conococheague  limestone,  the  rocks  may  be  conveniently  grouped  for 
purposes  of  study  into  three  divisions.  First,  a  basal  division  of  250  feet 
of  oolite,  edgewise  conglomerate  and  Cryptozoon  reefs;  second,  the  main 
mass  of  the  formation  about  1000  feet  or  more  in  thickness  made  up  of  the 
usual  banded  limestone;  and  third,  an  upper  part  of  400  feet  which  con- 
tains pink  marbles  in  addition  to  the  usual  rocks  of  the  formation.  All 
three  divisions  are  indicative  of  shallow  water  conditions  during  their 
deposition,  but  the  basal  beds  are  particularly  so.  The  edgewise  con- 
glomerate and  the  oolites  are  shallow  water  deposits  and  the  rounded 
grains  of  quartz  occurring  with  them  indicate  nearby  land.  In  these 
beds  are  also  inclusions  of  red  clay  which  closely  resemble  clays  resulting 
from  the  surface  weathering  of  limestone.  The  most  interesting  residual 


80        THE  CAMBRIAN  AND  OKDOVICIAN  DEPOSITS  OF  MARYLAND 

product  of  these  basal  beds  is  a  scoriaceous  chert  which  occurs  in  great 
quantity  in  the  soils  derived  from  their  weathering.  These  chert  masses 
are  sometimes  several  feet  in  diameter,  and  while  they  are  composed  of 
crystalline  milky  quartz,  they  are  so  iron  stained  and  cavernous  that  they 
have  the  appearance  of  slag  or  volcanic  material.  Fences  composed  of 
this  chert  are  not  uncommon  in  both  the  northern  and  southern  areas  of 
outcrops  and  they  are  good  evidence  that  the  dividing  line  between  the 
Elbrook  and  Conococheague  formations  is  close  at  hand.  Good  examples 
of  such  fences  may  be  seen  on  the  Antietam  battle-field  just  north  of 
Sharpsburg  along  the  Hagerstown  turnpike. 

The  main  mass  of  the  formation  is  described  in  preceding  paragraphs. 
The  upper  beds  of  pink  marble  are  very  much  like  similar  strata  in  the 
overlying  Beekmantown  limestone.  However,  there  is  no  occasion  to 
confuse  the  two  since  the  usual  siliceous  banded  rocks  of  the  Conoco- 
cheague are  intercalated  with  these  purer  strata.  Besides,  the  soils 
derived  from  these  upper  beds  contain  abundant  fragments  of  black  to 
yellow  chert  and  milky  vein  quartz.  Such  siliceous  residuals  are  char- 
acteristic of  the  Conococheague,  but  not  of  any  part  of  the  Beekmantown. 

The  above  remarks  apply  particularly  to  the  formation  as  developed 
east  of  the  Massanutten  syncline.  West  of  the  great  shale  belt  in  Mary- 
land the  general  features  of  this  limestone  remain  about  the  same,  with 
the  exception  that  600  or  more  feet  of  massive  sandy  dolomite  are  inter- 
calated between  the  usual  sandy  laminated  limestones  and  the  overlying 
Beekmantown  limestone.  These  sandy  dolomites  weather  into  sandstones 
which  strew  the  ground  with  large  and  small  blocks.  These  sandstones 
are  coherent  enough  at  times  to  have  been  used  in  the  past  as  a  local 
source  of  grindstones.  More  extended  study  in  neighboring  states  will 
probably  show  that  these  upper  sandy  dolomites  represent  the  eastward 
extension  of  strata  which  do  not  really  belong  with  the  typical  Conoco- 
cheague limestone.  However,  until  such  studies  have  been  made  it  is 
thought  advisable  to  classify  these  upper  sandy  beds  provisionally  with 
the  Conococheague  limestone.  A  good  section  of  this  upper  member  may 
be  seen  in  the  Western  Maryland  Railway  cut  just  west  of  Charlton, 


MARYLAND  GEOLOGICAL  SURVEY 


CAMBRIAN  AND  ORDOVICIAN,  PLATE  X 


FlG.  I. — EXPOSURE  OF  CONOCOCHEAGUE  LIMESTONE  ON  EDGE,  ALONG  ROAD  NEAR  BAKERS- 
VILLE,  MARYLAND.  THE  CHARACTERISTIC  STRONGLY  CRINKLED,  SANDY  LAMINAE  ARE  WELL 
DEVELOPED. 


PlG.   2. — LOWER  CONOCOCHEAGUE   SCORIACEOUS    CHERT   EXPOSED   IN    FENCE   ALONG    HAGERS- 
TOWN  TURNPIKE  JUST  NORTH  OF  SHARPSBURG,  MARYLAND. 


MARYLAND  GEOLOGICAL  SURVEY  81 

Maryland.  East  of  the  Massanutten  syncline  these  sandy  strata  are 
known  only  in  the  western  part  of  the  broad  expanse  of  Conococheague 
limestone  south  of  Hagerstown. 

TOPOGRAPHY. — The  topographic  features  of  the  Conococheague  lime- 
stone are  not  as  distinctive  as  those  of  the  adjacent  formations,  still  its 
presence  is  indicated  by  relatively  minor  topographic  pecularities  that 
after  all  are  decidedly  characteristic.  The  siliceous  beds  at  the  base  of 
the  formation  are  most  resistant  to  weathering  and  as  a  result  give  rise 
to  a  line  of  low  hills  trending  in  the  direction  of  the  outcrops.  The 
considerable  amount  of  scoriaceous  chert  arising  from  the  weathering  of 
these  lower  beds  also  tends  to  form  highlands.  The  hills  formed  by  the 
siliceous  basal  beds  are  most  conspicuous  in  the  northeastern  part  of  the 
valley  in  Maryland  from  the  state  line  southeast  through  Bowman's  Mill 
to  Chewsville.  The  siliceous  character  of  the  upper  portion  of  this  forma- 
tion likewise  resists  weathering,  but  not  in  as  great  a  degree  as  the  lower 
division.  In  general  the  areas  of  Conococheague  limestone  are  somewhat 
elevated  and  exhibit  rugged  topography  in  comparison  with  the  adjoining 
formations.  Outcrops  of  the  limestone  are  numerous,  in  fact  foiling 
country  with  low  hills  and  numerous  rocky  exposures  is  its  characteristic 
feature  in  northern  Maryland,  but  in  the  broad  area  in  the  southern  part 
of  the  state  the  rocks  themselves  are  seldom  seen.  Here  the  land  is  well 
cultivated  and  all  evidence  of  the  outcrop  has  usually  been  removed.  The 
stone  fences,  however,  are  indicative  of  the  underlying  formation,  as  the 
rock  employed  in  them  has  usually  been  taken  from  neighboring  fields. 
Stone  fences  built  of  the  characteristically  banded  Conococheague  lime- 
stone are  a  sure  indication  of  the  presence  of  the  formation. 

AREAL  DISTRIBUTION. — The  Conococheague  limestone  forms  the  sur- 
face rock  of  a  comparatively  broad  area  in  the  eastern  half  of  the  Great 
Valley  in  Maryland,  little  interrupted  by  infolds  of  other  formations. 
This  is  bordered  on  the  east  by  the  older  Elbrook  formation,  the  line  of 
contact  being  quite  regular  except  in  the  northern  part  of  the  state  where 
faulting  brings  two  narrow  tongues  of  the  Elbrook  to  the  surface.  The 
western  boundary  of  this  area  is  less  regular  due  to  several  infolds  of  the 


82        THE  CAMBRIAN  AND  ORDOVICIAN  DEPOSITS  OF  MARYLAND 

Stonehenge  member  of  the  overlying  Beekmantown  limestone.  This  area 
of  outcrop  therefore  has  a  general  monoclinal  structure  since  younger 
beds  border  it  on  the  west  and  older  beds  pass  beneath  it  on  the  east.  East 
of  Hagerstown,  Security  on  the  west  and  Chewsville  on  the  east  mark 
the  boundaries  of  the  outcrop  which  averages  three  miles  in  width. 
Numerous  exposures  of  the  typical  limestone  may  be  seen  along  the 
Western  Maryland  Eailway  between  Chewsville  and  Security  and  at  the 
latter  place  the  large  quarry  of  the  Security  Cement  and  Lime  Company 
exhibits  a  considerable  section  of  the  upper  beds  (see  pi.  XII,  fig.  I). 
Leitersburg,  five  miles  northeast,  stands  on  a  rocky  ridge  of  Conoco- 
cheague  limestone,  the  rock  here  belonging  to  the  lowest  beds  as  evidenced 
by  the  scoriaceous  chert  found  in  abundance  in  the  vicinity.  South  of 
Hagerstown  the  width  of  the  belt  of  outcrop  increases  to  over  five  miles, 
and  a  wide,  unbroken  expanse  of  this  limestone  occurs  along  the  Potomac 
and  for  some  miles  northward.  In  many  places  here  the  beds  are  either 
very  gently  folded  or  almost  horizontal. 

In  the  western  half  of  the  Valley  the  outcrops  of  the  Conococheague 
consist  of  several  narrow  belts  of  strata  brought  to  the  surface  in  the 
lowland  area  between  the  shale  highland  on  the  east  and  the  front  range 
of  the  Alleghenies  on  the  west.  Here  the  areas  of  outcrop  are  marked  by 
many  chert  fragments  and  sandstone  debris  left  in  the  soil. 

AGE  AND  COERELATION. — Only  a  small  number  of  species  of  fossils  has 
so  far  been  discovered  in  the  Conococheague  limestone,  these  consisting 
of  calcareous  algae  occurring  in  the  basal  beds;  several  brachiopods  and 
trilobites  found  in  the  upper  strata,  and  a  large  species  of  alga  near  the 
top  of  the  formation.-  The  two  calcareous  algae  (Cryptozoon  proliferum 
Hall  and  C.  undulatum  new  species)  at  the  base  of  the  formation  are 
found  in  abundance  wherever  these  beds  are  exposed.  The  large  Crypto- 
zoon near  the  top  is  a  not  uncommon  fossil,  but  the  trilobite,  Saukia 
stosei  Walcott,  and  the  brachiopod,  Eoorthis  cf.  desmopleura  (Meek),  are 
of  very  rare  occurrence  in  the  higher  beds.  The  trilobite  has  been  found 
only  in  the  Cumberland  Valley,  so  it  is  of  little  value  for  exact  correlation. 
Still  it  belongs  to  a  genus  that  is  elsewhere  represented  only  in  late  Upper 


MARYLAND  GEOLOGICAL  SURVEY 


CAMBRIAN  AND  ORDOVICIAN,  PLATE  XI 


"EDGEWISE  BEDS"  CHARACTERISTIC  OF  BEEKMANTOWN  (UPPER  RIGHT  HAND 
FIGURE)  AND  CONOCOCHEAGUE  FORMATIONS  (LOWER  FIGURE),  HAGERSTOWN  VALLEY, 
WASHINGTON  COUNTY.  THE  UPPER  LEFT  HAND  FIGURE  REPRESENTS  THE  CHARAC- 
TERISTIC FINELY  LAMINATED  FEATURE  OF  THE  BEEKMANTOWN  LIMESTONE. 


MARYLAND  GEOLOGICAL  SURVEY  83 

Cambrian  and  Middle  Ozarkian  formations.  Moreover,  its  affinities  lie 
nea-rer  the  Ozarkian  species  than  the  Cambrian,  so  that  its  evidence,  so  far 
as  it  goes,  favors  assignment  of  the  Conococheague  to  the  Lower  Ozarkian. 
Vhe  brachiopod,  also,  as  now  understood,  has  too  wide  a  range  for  detailed 
stratigraphic  work.  The  two  species  of  Cryptozoon  at  the  base  occupy  this 
position  throughout  a  large  part  of  the  Appalachian  Valley  and  serve  as 
excellent  guide  fossils. 

The  Maryland  early  Paleozoic  section  is  far  from  complete  and  the 
age  of  the  Conococheague  limestone  must  be  determined  from  more  fully 
developed  sections  in  other  areas.  The  Cryptozoon  fauna  occurs  in  central 
Pennsylvania  in  the  Gatesburg  dolomite  which,  roughly  speaking,  is  the 
equivalent  of  the  Conococheague  limestone.  Beneath  the  Gatesburg  dolo- 
mite, and  separating  it  from  the  Middle  Cambrian,  Elbrook,  is  an  Upper 
Cambrian  formation,  the  Warrior  limestone.  To  the  south  in  Virginia, 
Tennessee,  and  Alabama,  the  same  Cryptozoon  fauna  is  also  known  and  in 
each  case  it  is  separated  from  the  Middle  Cambrian  equivalents  of  the 
Elbrook  limestone  by  Upper  Cambrian  formations  of  great  thickness  and 
containing  well-developed  faunas.  Evidently  then  we  must  conclude  that 
the  contact  between  the  Elbrook  and  Conococheague  in  Maryland  is 
unconformable  and  represents  a  stratigraphic  break  of  considerable 
magnitude. 

Cryptozoon  Reefs. 

The  basal  15  or  20  feet  of  the  Conococheague  limestone  usually  exhibit 
layers  so  uniformly  and  curiously  laminated  over  considerable  areas  that 
this  phenomenon  cannot  be  attributed  to  ordinary  plications  in  the  strata. 
All  of  the  sandy  laminated  and  banded  portions  of  the  formation  show  a 
wavy  or  crinkled  structure,  especially  where  strong  folding  has  occurred, 
but  the  laminations  of  the  basal  beds  are  of  a  quite  different  nature.  The 
limestones  in  which  the  latter  laminated  structures  occur  are  not  of  the 
usual  banded  type,  but  are  composed  of  a  massive,  rather  homogeneous 
and  somewhat  purer  rock.  In  an  edge  view  of  a  stratum  the  rock  is  seen 
to  be  made  up  of  thin,  parallel  films  of  material  piled  one  upon  the  other. 


84        THE  CAMBRIAN  AND  ORDOVICIAN  DEPOSITS  OF  MARYLAND 

At  first  these  films  are  practically  horizontal  to  the  bedding  planes,  but 
soon  undulation  commences  and  narrow  or  broad  folds  with  narrower  or 
sharper  bending  down  of  the  films  occurs.  After  an  interval  of  several 
inches  exhibiting  such  undulation,  the  horizontal  lamination  is  resumed 
and  this  in  turn  is  followed  by  a  repetition  of  the  undulations.  These 
wavy  outlines  as  seen  in  cross-sections  of  the  strata  appear  as  concen- 
trically lined  areas  of  varying  diameter  on  the  bedding  planes  themselves. 
The  greater  the  width  of  the  fold  seen  in  transverse  section,  the  greater 
the  diameter  of  the  corresponding  concentric  area. 

These  laminated  strata  at  the  base  of  the  Conococheague  follow  two 
distinct  patterns.  In  each  the  basal  laminae  are  horizontal  to  the  bedding 
plane,  but  the  succeeding  undulations  are  quite  different.  In  one  kind 
the  undulations  are  an  inch  or  less  across  and  retain  this  diameter 
uniformly.  In  the  other,  the  width  of  the  undulations  varies  from  a 
central  one,  several  inches  across  to  lateral  ones  an  inch  or  less  wide. 
Upon  the  weathering  of  the  surrounding  strata,  masses  of  this  laminated 
rock  are  left  in  the  soil,  still  retaining  their  calcareous  composition  or,  as 
is  more  frequently  the  case,  changed  to  silica.  In  either  case  the  uni- 
formity in  shape  of  these  residual  masses  would  seem  to  indicate  that 
they  are  definite  organic  structures. 

Walcott  has  described  a  number  of  quite  similar  laminated  structures 
from  the  Proterozoic  rocks  of  the  West  and  has  shown  that  they  represent 
the  secretions  of  calcareous  algae.  Certain  of  the  Proterozoic  limestones 
contain  beds  crowded  with  these  algal  structures  which  are  repeated  again 
and  again  through  thousands  of  feet  of  strata.  These  remains  are  not 
those  of  the  fossil  plant  itself,  but  are  simply  the  secretions  of  calcium 
carbonate  upon  the  tissue  of  the  plant.  As  is  well  known,  calcium 
carbonate  held  in  solution  by  an  excess  of  carbon  dioxide  in  the  water 
is  deposited  when  the  carbon  dioxide  is  abstracted.  In  securing  carbon 
from  the  carbon  dioxide  for  the  building  of  their  tissues  the  lime  is 
deposited  upon  the  films  of  the  plant  which  abstracts  the  carbon  dioxide. 
The  form  of  the  plant,  however,  is  well  preserved  in  these  limestone 
secretions. 


MARYLAND  GEOLOGICAL  SURVEY 


CAMBRIAN  AND  ORDOVICIAN,  PLATE  XII 


FlG.   I. — QUARRY  IN  UPPER  PART  OF  CONOCOCHEAGUE  LIMESTONE  WITH   SECURITY  CEMENT 
WORKS,   SECURITY,   MARYLAND,   IN   DISTANCE. 


FlG.  2. — TYPICAL  EXPOSURE  OF  THE  LOWER  PURE  FINELY  CONGLOMERATIC  BEDS  OF  THE 
STONEHENGE  LIMESTONE  ALONG  NATIONAL  HIGHWAY,  JUST  SOUTH  OF  FUNKSTOWN, 
MARYLAND. 


MARYLAND  GEOLOGICAL  SURVEY  85 

The  Proterozoic  forms  of  calcareous  algae  have  been  described  under 
six  genera,  but  all  of  the  Cambrian  and  Early  Ordovician  forms  have  been 
referred  to  the  single  genus  Cryptozoon.  The  basal  Conococheague 
species,  consisting  of  a  wide,  flat  basal  portion  of  laminae  growing  into 
numerous  head-like  masses  large  at  the  center  and  small  along  the  edges, 
was  described  long  ago  by  Hall  as  Cryptozoon  proliferum.  The  second 
species,  with  laminae  of  equal  undulations,  is  described  in  this  volume 
as  new. 

These  two  types  of  structure  are  often  associated  together  in  such 
numbers  that  they  form  a  true  reef.  Sometimes  only  one  of  the  species 
will  be  represented  in  the  reef,  though  occurring  in  such  great  numbers 
as  to  completely  fill  the  rock.  A  reef  composed  entirely  of  Cryptozoon 
proliferum  is  well  exposed  in  a  cut  along  the  Norfolk  and  Western  Bail- 
road  about  one  mile  southwest  of  Antietam  Station,  Maryland  (see 
pi.  IX,  fig.  1),  where  the  highly  tilted  limestones  expose  the  individual 
colonies  of  the  alga  to  good  advantage.  Similar  reefs  of  C.  proliferum 
were  observed  along  the  northern  line  of  outcrop  from  the  state  line  south- 
east to  Chewsville.  The  base  of  the  line  of  low  hills  about  a  mile  west  of 
Ringgold  gives  numerous  specimens  of  this  species.  The  outcrops  of  the 
basal  beds  along  the  line  five  miles  southeast  of  Hagerstown  show  reefs 
of  the  new  species  Cryptozoon  undulatum  most  commonly. 

These  reefs  of  calcareous  algae  are  of  interest  and  practical  value  from 
the  standpoint  of  structural  geology  because  they  afford  an  exact  criterion 
for  determining  the  top  or  bottom  of  a  stratum.  In  areas  of  highly  folded 
strata  such  as  the  Appalachian  Valley,  this  determination  is  frequently 
highly  important  and  sure  methods  are  few.  The  broad  upfolds  of  the 
laminations  and  the  narrow  sharp  down  folds  register  the  upper  and 
lower  sides  respectively  of  the  stratum  without  a  doubt. 

Still  a  third  type  of  strongly  laminated  Cryptozoon  structure  occurs 
near  the  top  of  the  Conococheague  limestone  in  both  the  eastern  and 
western  areas  of  outcrop  in  Maryland.  No  specimens  have  been  obtained 
free  from  the  matrix,  but  natural  sections  in  the  rock  show  that  the 
undulations  are  18  or  more  inches  in  width  and  that  the  zone  of  strong 


86        THE  CAMBRIAN  AND  ORDOVICIAN  DEPOSITS  OF  MARYLAND 

undulations  rises  in  the  stratum  to  a  height  of  two  feet  or  more.  This 
Cryptozoon  sometimes  consists  of  a  single  mass  of  strongly  marked  undu- 
lating layers  one-half  inch  apart  rising  in  the  rock  like  a  column.  Speci- 
mens may  be  seen  to  advantage  two  miles  northwest  of  Leitersburg  along 
the  road  south  of  Millers  Chapel,  and  along  the  Western  Maryland  Rail- 
road just  west  of  Charlton,  Maryland.  This  particular  Cryptozoon  is  of 
special  interest  in  having  oolites  one-eighth  of  an  inch  in  diameter 
abundantly  developed  in  the  areas  between  the  dow'nfolds  of  the  lamina- 
tions (see  pi.  IX,  fig.  2).  The  formation  of  these  oolites  appears  to  have 
been  connected  with  the  life  activities  of  the  plant. 

Edgewise  Conglomerate. 

These  peculiar  conglomerates  are  such  a  marked  feature  of  the  Conoco- 
cheague  limestone  that  they  are  described  at  this  point,  although  they 
occur  equally  well  developed  in  subsequent  formations.  The  typical  dark- 
blue,  banded  and  frequently  crinkled  limestones  of  the  Conococheague 
formation,  are  often  separated  by  layers  varying  from  a  few  inches  to  a 
foot  or  more  in  thickness,  composed  of  a  rather  homogeneous  or  slightly 
granular  rock  filled  with  long,  slender  fragments  of  a  distinctly  different 
limestone  tilted  at  various  angles  to  the  bedding  plane.  The  actuality  of 
the  difference  in  composition  of  the  two  rock  types  making  up  such  layers 
is  not  conspicuously  evidenced  on  a  freshly  fractured  surface,  but  weather- 
ing causes  the  slender  fragments  to  stand  out  quite  prominently  upon 
exposed  surfaces.  The  position  of  the  fragments  frequently  on  end  or  on 
edge  in  the  matrix  has  given  the  common  name  of  edgewise  beds  to  such 
strata.  Some  of  these  fragments  are  sharp-edged  and  show  no  evidence 
of  wave  action ;  others  are  rounded  at  one  or  both  ends  and  have  appar- 
ently been  worn.  Often  the  matrix  of  these  conglomerates  contain  small, 
rounded  quartz  grains,  evidently  derived  from  some  nearby  land  area. 

These  edgewise  beds  have  long  been  considered  as  intraformational 
conglomerates  and  under  a  broad  definition  of  that  term  they  could  still 
be  considered  so.  However,  the  original  intraformational  conglomerate 
described  by  Walcott  did  not  include  this  type.  All  of  his  examples  are 


MARYLAND  GEOLOGICAL  SURVEY  87 

more  of  the  nature  of  real  conglomerates  even  though  the  fragments  of 
which  they  consist  are  of  the  same  age  as  the  surrounding  matrix  and 
are  not,  as  an  ordinary  conglomerate,  composed  of  foreign  rocks. 

Although  these  curious  edgewise  structures  have  been  known  to  geolo- 
gists for  many  years,  little  mention  of  them  has  been  made  in  the  literature 
until  comparatively  recently.  The  term  "  edgewise "  was  coined  by 
Kason  in  1901 1  and  the  occurrence  of  such  structures  was  mentioned  by 
Bain  and  Ulrich  in  1905. 2  In  1906  Seely  described  the  edgewise  con- 
glomerate in  division  D  of  the  Beekmantown  limestone  in  the  Champlain 
Valley  as  the  "Wing  Conglomerate,"  naming  it  after  Mr.  Wing  who 
made  the  original  observations  upon  it. 

Seely  believed  that  these  flat  pebbles  could  not  be  laid  down  in  either 
swift  or  slow  water  in  the  position  they  are  now  found  and  came  to  the 
conclusion  that  they  were  organic.  He  described  them  as  three  species  of 
the  genus  Wingia,  a  new  genus  of  Beekmantown  sponges. 

Stose,  in  1910,  in  the  Chambersburg-Mercersburg  folio  of  the  U.  S. 
Geological  Survey,  mentioned  these  conglomerates  and  ascribed  their 
origin  to  the  breaking  up  of  freshly  deposited  thin-bedded  lime  sediment 
by  shallow-water  wave  action  into  shingle  or  flat  fragments  that  were 
shuffled  about  on  the  beach.  T.  C.  Brown,8  in  an  article  on  the  origin  of 
certain  Paleozoic  sediments,  reverted  to  the  organic  origin  of  the  pebbles, 
but  concluded  they  resulted  from  the  activities  of  calcareous  algae.  He 
admitted  that  no  specimens  preserving  any  organic  structure  sufficiently 
well  to  prove  their  origin  had  been  found.  Another  interesting  origin  for 
these  conglomerates  is  that  discussed  by  Grabau  in  his  Principles  of 
Stratigraphy  where  he  explains  that  they  are  due  to  deformation  through 
gliding  which  has  resulted  in  the  complete  brecciation  of  the  layers.  He 
distinguishes  the  intraformational  conglomerates  in  which  the  fragments 
lie  in  all  positions,  and  the  edgewise  conglomerate  where  the  gliding 
process  has  caused  the  thin  cakes  to  assume  a  vertical  position  in  the  rock 

1  Amer.  Jour.  Sci.,  4th  ser.,  vol.  12,  p.  360. 

2  Copper  deposits  of  Missouri,  Bull.  267,  U.  S.  Geological  Survey,  p.  23. 

3  Journal  of  Geology,  vol.  xxiii,  No.  3,  1913. 


88        THE  CAMBRIAN  AND  ORDOVICIAN  DEPOSITS  or  MARYLAND 

mass.    No  such  distinction  as  this  can  be  drawn  in  nature  because  there 
are  all  gradations  of  arrangement. 

The  observations  of  Ulrich,  Stose,  Butts  and  other  geologists  who  have 
had  numerous  opportunities  to  study  the  edgewise  beds,  all  tend  to  the 
conclusion  that  these  conglomerates  are  not  organic;  but  are  composed  of 
fragments  formed  on  tidal  flats  by  mud  cracks.  The  Appalachian  early 
Paleozoic  formations  are  practically  all  shallow-water  deposits  in  which 
the  area  was  often  subject  to  uplift  above  the  sea  level.  Mud  flats  which 
by  uplift  are  exposed  to  evaporation  soon  develop  the  usual  shrinkage 
figures  known  as  sun  cracks  and  the  edges  of  these  to-day  curl  up  and  are 
broken  off  and  tossed  about  by  the  wind.  This  same  condition  has 
occurred  time  and  again  in  the  past,  and  indeed  limestones  still  preserving 
well-defined  sun  cracks  with  the  edges  curled  up  and  ready  to  be  formed 
into  edgewise  conglomerates  have  been  observed. 

FOSSILS  OF   CAMBRIAN  AGE 

In  spite  of  the  considerable  thickness  of  Cambrian  rocks  developed  in 
the  Appalachian  region  of  Maryland,  and  the  careful  search  that  has  been 
made,  fossils  of  this  age  are  exceedingly  rare.  Usually  no  trace  of 
organisms  can  be  detected  in  the  rocks,  and  the  few  specimens  noted  have 
always  been  fragmentary  and  poorly  preserved.  These  few  remains  occur 
in  the  Harpers  schist,  Antietam  sandstone,  and  Tomstown  limestone  of 
Lower  Cambrian  age,  in  the  two  Middle  Cambrian  formations,  the 
Waynesboro  formation  and  Elbrook  limestone  and  in  the  Upper  Cambrian 
(Ozarkian),  Conococheague  limestone.  The  basal  Cambrian  Loudon 
formation  and  the  succeeding  Weverton  quartzite  are  lithologically  of 
such  a  nature  that  fossils  would  not  be  expected  in  them,  but  the  over- 
lying formations  are  more  promising  in  this  respect  and  may  possibly 
yield  to  some  fortunate  collector  more  respresentative  faunas  than  known 
at  present.  Fairly  well-developed  Lower  and  Middle  Cambrian  faunas 
are  known  in  the  Appalachians  both  north  and  south  of  Maryland,  but  it 
appears  that  the  strata  bearing  them  are  usually  not  represented  in  the 
Maryland  section.  For  example,  the  Lower  Cambrian  strata  at  York, 


MARYLAND  GEOLOGICAL  SURVEY  89 

Pennsylvania,  containing  well-preserved  trilobites,  do  not  appear  to  be 
present  in  Maryland. 

The  few  species  thus  far  discovered  in  the  Conococheague  limestone  of 
southern  Pennsylvania  and  Maryland  give  no  idea  of  the  characteristics 
of  the  Upper  Cambrian  (Ozarkian)  faunas.  It  is  true  that  the  two 
species  of  Cryptozoon  are.  characteristic  Ozarkian  fossils  over  a  wide  area, 
but  very  similar  species  are  found  in  the  succeeding  Ordovician  strata. 
The  single  species  of  trilobite  is  very  limited  in  its  distribution  and  the 
brachiopod  is  too  little  restricted  to  be  of  any  stratigraphic  value. 

The  few  Cambrian  species  identified  in  Maryland  strata  are  described 
in  the  following  pages.  These  species  are  listed  below  under  their 
appropriate  formations : 

Lower  Cambrian  (Waucoban)  Fossils  of  Maryland 

Harpers  shale.    Scolithus  linearis  Haldemann. 

Antietam  sandstone.    Scolithus  linearis  Haldemann,  Obolella  minor  (Walcott), 

Hyolithes  communis  Billings,  and  Olenellus  thompsoni  (Hall). 
Tomstown  limestone.    Olenellus  thompsoni  (Hall)  and  Salterella  sp. 

Middle  Cambrian   (Acadian)   Fossils 

Waynesboro  formation.    Lingulella  sp. 
Elbrook  formation.    Dolichometopus  sp. 

Upper  Cambrian  (Ozarkian)   Fossils 
Conococheague  Limestone 

Cryptozoon  proliferum  Hall  (common  at  base) 
Cryptozoon  undulatum  n.  sp.  (common  at  base) 
SauJcia  stosei  Walcott  (rare  in  upper  part) 
Eoorthis  desmopleura  (Meek)  (rare  in  upper  part) 

THE    BEEKMANTOWN    LIMESTONE 

The  middle  part  of  the  Appalachian  Valley  in  Maryland,  with  the 
exception  of  the  Martinsburg  shale  belt  which  is  three  miles  in  width, 
and  small  areas  or  other  formations,  is  directly  underlain  by  a  thick  mass 
of  rather  pure  limestone.  Nearly  all  of  this  rock  is  fine  grained  and  most 
of  it  is  minutely  laminated.  Interbedded  with  these  are  pure  minutely 


90        THE  CAMBRIAN  AND  ORDOVICIAN  DEPOSITS  or  MARYLAND 

laminated  limestones  with  some  layers  containing  occasional,  more  or  less 
massive.,  ledges  in  which  the  lamination  is  obscure.  Some  of  these  con- 
tain numerous  poorly  preserved  fossils.  Study  of  these  fossils  shows  that 
a  large  part  of  the  local  fauna  consists  of  species  previously  found  in  the 
Beekmantown  limestone  of  the  Champlain  Valley  in  New  York,  Vermont, 
and  southeastern  Ontario.  In  1910  *  the  northern  extension  of  these 
strata  was  distinguished  and  separately  mapped  under  the  same  name  by 
which  the  formation  is  known  in  New  York. 

The  Frederick  Valley  in  Maryland,  east  of  the  Blue  Ridge,  also  con- 
tains a  considerable  development  of  rather  pure  massive  limestone  hold- 
ing Beekmantown  fossils.  This  development  of  the  Beekmantown  is 
discussed  in  a  separate  chapter,  so  that  the  following  description  of  the 
stratigraphy  applies  only  to  the  Appalachian  Valley.  As  a  whole,  the 
Beekmantown  limestone  of  Maryland  is  quite  distinct  lithologically  from 
the  other  divisions  of  the  Shenandoah  group,  although  the  occurrence  of 
similar  beds  in  most  of  the  formations  often  causes  difficulty  in  the 
recognition  of  isolated  outcrops.  Its  strata  are  most  likely  to  be  confused 
with  the  underlying  Conococheague  limestone,  because  edgewise  con- 
glomerates are  not  uncommon  in  the  Beekmantown,  in  fact  in  the  upper 
half  of  the  lowest  division  they  are  as  well  developed  as  in  the  Conoco- 
cheague limestone.  The  characteristic  sandy  laminated  banded,  dark 
blue  rock  of  the  latter,  excepting  one  bed,  is  not  developed  in  the  Beek- 
mantown. The  main  mass  of  the  Beekmantown  formation  is  of  finely 
laminated,  lighter  colored  and  purer  rock  than  occurs  in  the  Conoco- 
cheague. The  successive  beds  also  are  more  uniform  in  texture,  color  and 
composition.  On  this  account,  it  is  difficult  to  distinguish  the  different 
portions  above  the  basal  division,  which  contains  the  exception  mentioned 
above  in  which  siliceous  banded  limestones  occur. 

Fortunately  there  are  four  fossiliferous  zones  in  the  formation  with 
characteristic  species  in  each,  which  appear  frequently  enough  in  the 
outcrops  to  obviate  some  of  the  difficulties  of  determination.  Several 
distinct  zones  in  this  formation  may  also  be  recognized  by  residual 

1  Chambersburg-Mercersburg  folio,  U.  S.  Geological  Survey. 


92        THE  CAMBRIAN  AND  ORDOVICIAN  DEPOSITS  or  MARYLAND 

products  left  in  the  soil  by  the  weathering  of  the  limestone.  The  top, 
middle  and  lower  portions  are  especially  well  characterized  by  siliceous 
products,  such  as  chert,  flint  and  sandy  shale  fragments,  which  are  dis- 
cussed in  detail  in  succeeding  paragraphs.  • 

LITHOLOGIC  •  CHARACTER. — Although  the  Beekmantown  limestone 
differs  considerably  in  its  lithological  development  in  the  eastern  and 
western  parts  of  the  valley,  the  formation  as  a  whole  is  composed  of 
much  purer  limestones  than  the  underlying  Conococheague.  On  the  other 
hand  its  purest  beds  are  inferior  in  calcium  carbonate  content  to  the  high 
average  of  the  overlying  Stones  Kiver  limestone.  The  purer  limestones 
of  the  Beekmantown  are  interbedded  with  greater  thickness  of  relatively 
impure  finely  laminated  beds  which  occur,  or  at  least  outcrops,  so  fre- 
quently that  the  presence  of  these  laminated  limestones  is  a  good  criterion 
for  the  formation.  This  characteristic  minute  lamination  of  the  average 
rock  of  the  formation  is  due  to  impurities  in  the  rock  and  most  apparent 
on  weathered  surfaces.  Pink  and  white  fine  grained  marbles  in  ledges  of 
considerable  thickness  also  are  of  common  occurrence  in  the  Beekman- 
town, especially  in  the  lower  half  of  the  formation.  Marbles  occur  in  the 
underlying  Conococheague  limestone,  but  as  they  are  always  associated 
with  the  characteristic  siliceous  banded  limestone  of  that  formation  they 
are  readily  distinguished  from  the  marble  beds  of  the  Beekmantown.  But 
it  should  not  be  forgotten  that  siliceous  banded  limestones  quite  similar 
to  those  of  the  underlying  Conococheague  beds  occur  also  in  the  lower 
fifth  of  the  Beekmantown.  These  are  so  constantly  developed  in  tho 
eastern  half  of  the  valley  that  the  part  containing  them  has  been  mapped 
as  a  distinct  basal  division  under  the  name  of  the  Stonehenge  limestone 
member.  This  basal  member  can  be  recognized  locally  also  in  the  western 
part  of  the  valley,  but  here  its  lithologic  characters  are  hardly  distinct 
enough  to  warrant  its  separation  in  the  mapping. 

As  practically  all  of  the  Beekmantown  areas  of  Maryland  are  covered 
by  gently  rolling  cultivated  farm  lands  it  is  almost  impossible  to  make 
out  the  complete  section  of  the  formation  in  any  particular  place.  How- 
ever, by  assembling  incomplete  sections  in  various  parts  of  the  valley  the 


MARYLAND  GEOLOGICAL  SURVEY  93 

following  generalized  section  for  Maryland  and  southern  Pennsylvania 
lias  been  described  by  Ulrich  in  his  Revision  of  the  Paleozoic  Systems : ' 

Generalized  Section  of  Beekmantown  Limestone  in  Southern  Pennsylvania 

and  Maryland 

Feet 
Base  of  Stones  River  limestone  with  quartz  pebble  conglomerate  and 

cauliflower  chert 

Hard  dense  white  chert  and  granular  quartzose  chert  forming  by 

secondary  silicification,  cauliflower  chert 40 

Fine  grained  gray,  finely  laminated,  interbedded  pure  and  magneslan 
unfossiliferous  limestone  with  sandy  chert  and  limestone  and 

dolomite  conglomerates  at  the  top 400 

Turritoma  zone.    Thin  bedded  argillaceous  and  massive  purer  limestone 
containing  the  Turritoma  fauna.    Many  of  the  beds  weather  so 
as  to  appear  riddled  with  worm  borings 200 

Alternating  beds  of  pure  dove,  pure  gray  and  magnesian  gray  unfos- 
siliferous limestone  often  laminated,  with  occasional  beds  of  fine 
limestone  conglomerate 300 

Massive  pure  dove  gray  and  magnesian  limestone  terminated  above 
by  sandy  fossiliferous  chert  containing  Syntrophia  later  alls, 

Maclurites  sordida  and  species  of  Liospira 75 

Ceratopea  zone.  Blue  and  dove  fossiliferous  limestone  cherty  in  the  upper 
half,  containing  Ceratopea  and  associated  fossils.  At  the  base  is 

a  blue  limestone  filled  with  rounded  quartz  grains 250 

Cryptozoon  steeli  zone.    Fine  grained  nearly  pure  limestone  with  some 

magnesian  beds  and  several  layers  of  porous  chert 275 

Dove,  pink  and  bluish  fine  grained  pure  limestone  and  marble 300 

Oolitic,  cherty  blue  and  gray  limestone  holding  the  Cryptozoon  steeli 

fauna  and  weathering  into  platy  yellow  chert 60 

Stonehenge  limestone  member.  Massive  dark  blue  to  gray  limestone  with 
contorted  argillaceous  and  siliceous  laminations  weathering  to 
sandy  shale,  interbedded  with  edgewise  beds  and  oolites 250 

Massive  blue  to  gray  pure  limestone  weathering  white,  with  cepha- 

lopods  and  gastropods  occurring  in  reef  structures 250 

Top  of  Conococheague  limestone  with  sandy  laminae  and  beds  of  edgewise 

conglomerate    


2400 

From  the  stratigraphic  standpoint  the  important  divisions  of  the  above 
section  are  the  Stonehenge  member  and  the  three  zones  marked  respec- 
tively the  Cryptozoon  steeli,  Ceratopea,  and  Turritoma  zones.  The  faunal 
and  other  characteristics  of  these  zones  are  discussed  in  succeeding 
paragraphs. 

1  Bull.  Geol.  Soc.  America,  vol.  xxii.  No.  3,  1911,  pp.  652-655. 


94        THE  CAMBRIAN  AND  ORDOVICIAN  DEPOSITS  or  MARYLAND 

While  the  general  section  given  above  holds  fairly  well  for  all  parts 
of  the  Valley,  the  detailed  stratigraphy  of  the  formation  in  the  eastern 
and  western  parts  is,  as  mentioned  above,  somewhat  different.  The  best 
exposure  of  the  Beekmantown  limestone  east  of  the  Martinsburg  shale 
belt  is  adjoining  the  Chambersburg-Gettysburg  Pike  one  mile  east  of 
Chambersburg,  Pennsylvania.  This  section,  measured  by  Ulrich  and 
Stose,  is  given  below  with  slight  emendations  to  show  the  position  of  the 
fossil  zones. 

Section  of  Beekmantown  Limestone  One  Mile  East  of  Chambersburg, 

Pennsylvania 

Feet 

Base  of  Stones  River,  containing  fine  limestone  conglomerate  and  laminar 

and  oolitic  chert 

Interbedded  fine-grained  pure  and  magnesian  limestones,  finely  laminated 
in  part  and  containing  small  quartz  geodes;  porous  sandy  chert  near 
top;  dark-blue  layers  near  base  containing  numerous  gastropods 
(Turritoma  fauna)  and  ostracods  and  mottled  by  magnesian  material 
that  weathers  out,  leaving  pits  and  holes 600 

Alternating  pure  dove-colored  and  gray  limestone  and  magnesian  lime- 
stone, with  layer  of  sandy  chert 375 

Bluish  to  dove-colored  fine-grained  fossiliferous  limestone,  at  the  base 

containing  rounded  quartz  grains.    Ceratopea  fauna  at  top 100 

Pink  fine-grained  marble,  containing  layers  of  milky  quartz  chert; 
gastropods'  of  the  genera  Ophileta,  Maclurites  and  Eccyliopterus 
rather  abundant 275 

Pure  dove-colored  and  blue  fine-grained  limestone,  with  some  pink  lime- 
stones; contains  fragments  of  trilobites 285 

Fine-grained  dove-colored  to  dark  gray  limestone  with  fine  conglomerate 
and  oolite  beds;  abundant  chert  in  upper  portion,  in  part  oolitic  and 
conglomeratic.  Cryptozoon  steeli  in  middle  part 145 

Stonehenge  limestone  member:  .' 

Fine-grained  light  to  dark  gray  limestone  containing  wavy  laminae 
of  sandy  matter  that  stand  in  relief  or  fall  to  sandy  shale  on 
weathering  and  thick  beds  of  "  edgewise  "  conglomerate;  gastro- 
pods in  upper  and  fine  fragments  of  trilobites  in  lower  portion. .     225 
Dark  to  very  light  gray  massive  limestone,  containing  Dalmanella, 

Ophileta  and  trilobite  fragments 260 

Top  of  Conococheague,  containing  wavy  and  sandy  laminae  and  beds  of 

coarse  limestone  conglomerate 


2265 

"West  of  the  shale  belt,  the  details  of  the  Beekmantown  section  are 
somewhat  different,   although  the  several  fossil  zones  can  be   readily 


MARYLAND  GEOLOGICAL  SURVEY  95 

recognized.  No  continuous  well-exposed  section  of  these  strata  was  noted 
in  Maryland,  and  the  section  repeated  below  is  one,  published  by  Ulrich 
and  Stose,1  of  the  northern  continuation  of  the  formation  in  southern 
Pennsylvania.  This  section  is  broken  and  probably  incomplete  480  feet 
beneath  the  base  of  the  overlying  Stones  Kiver  limestone.  If  the  Turri- 
toma  zone  which  was  not  observed  is  present  in  this  basin,  it  may  have 
been  faulted  out  or  is  concealed  by  covering  soil  and  debris.  However,  it 
has  been  recognized  in  the  southern  continuation  of  the  belt  in  Maryland. 

Section  of  Beekmantown  Limestone  near  Mouth  of  Licking  Creek, 
Franklin  County,  Pennsylvania 

Feet 

Interbedded  pure  and  magnesian  limestone  of  Stones  River  type 

Light-gray,  finely  laminated  magnesian  limestone  and  white  dolomite 

with  cherts  of  rosette  type  at  the  top 340 

Dark  and  light  coarse  dolomite 140 

Rocks  folded  and  largely  covered;  white  dolomite,  dark-blue  oolitic  lime- 
stone, and  dark  coarse  dolomite  with  yellow  blocky  sandstone  frag- 
ments and  rosette  cherts;  exact  continuity  indeterminable,  but  the 
previous  beds  are  apparently  repeated  by  folding 

Interbedded  pure  and  magnesian  limestone,  with  beds  of  coarse  dark 
dolomite,  and  in  the  lower  part  beds  of  "  edgewise  "  conglomerate;  at 
base  contains  Ceratopea  gastropods,  cephalopods,  and  trilobites 350 

In  large  part  finely  banded  magnesian  limestone  with  few  pure  lime- 
stones; contains  fine  conglomerate  beds  and  gastropods 170 

Largely  dolomite,  some  coarse  and  dark;  large  scoriaceous  black  chert 

and  coarse  sandstone  at  the  base 130 

Chiefly  dolomite,  coarse  and  dark  in  upper  part,  with  some  pure  fos- 
siliferous  limestone;  bed  of  granular  limestone  with  numerous 
Ophileta  and  pinkish  fine-grained  limestone  near  middle;  cross- 
bedded  banded  limestone  at  base,  locally  unconformable  on  under- 
lying beds 290 

Fine-grained  limestone  seamed  with  calcite  and  dolomite  beds  with  flinty 

chert  containing  Cryptozoon  steeli  at  the  base 65 

Partly  covered;  lower  part  pure  dark  limestone  with  a  few  beds  of  finely 
laminated  magnesian  limestone  and  fine  white  oolite  near  base;  small 
rough  chert  with  casts  of  crystals  at  the  base 130 

Light-blue  limestone  with  fine  contorted  sandy  laminae  that  weather  in 
relief;  contains  fine  dark  conglomerate  with  red  limestone  pebbles 
and  fragments  of  trilobites 165 

Purer  fine  even-grained  limestone  with  few  sandy  partings 530 

Sandy  laminated  limestone,  much  contorted  (Conococheague) 


2310 


1  Chambersburg-Mercersburg  folio  U.  S.  Geological  Survey. 

7 


96        THE  CAMBRIAN  AND  ORDOVICIAN  DEPOSITS  OF  MARYLAND 

Comparison  of  these  sections  brings  out  several  salient  differences  in 
the  lithology  of  the  two  areas.  East  of  the  shale  belt,  the  Stonehenge 
member  with  its  characteristic  siliceous  banded  limestone,  is  distinct 
enough  to  be  mapped  as  a  separate  unit,  but  west  of  that  belt  the  siliceous 
banding  of  the  lower  Beekmantown  is  not  so  well  developed.  However,  the 
same  faunas  are  present  in  these  strata  in  both  areas  so  that  there  is  no 
doubt  as  to  the  presence  of  beds  corresponding  to  the  Stonehenge  member 
in  both.  The  higher  beds  in  each  area  also  contain  similar  faunas,  but 
the  lithology  is  somewhat  different,  limestone  predominating  in  the  east 
and  dolomite  in  the  west.  Chert  in  large  quantities  weathers  from  certain 
portions  of  the  dolomite  in  the  western  area,  but  it  is  not  so  conspicuously 
developed  in  the  east. 

The  two  sections  illustrate  the  lithologic  changes  occurring  in  the 
formation  going  from  the  east,  where  over  three-fourths  of  the  formation 
consists  of  pure  limestone,  across  the  strike  to  the  western  side  of  the 
Valley  where  more  than  half  of  the  strata  is  more  or  less  highly  magnesian. 
In  Appalachian  areas  still  further  west,  as  in  central  Pennsylvania,  the 
change  to  magnesian  limestone  becomes  yet  more  pronounced. 

FAUNAL  ZONES. — Although  the  lithologic  features  of  the  various  por- 
tions of  the  Beekmantown  limestone  vary  considerably,  the  basal  member 
is  the  only  division  which  can  be  definitely  recognized  from  the  character 
of  its  strata.  Above  this  lower  division — the  Stonehenge  member — three 
distinct  fauna!  zones  aid  in  the  recognition  of  their  respective  horizons. 
These  are  in  ascending  order  above  the  Stonehenge  member,  the  Crypto- 
zoon  steeli  zone,  the  Ceratopea  zone  and  the  Turritoma  zone.  The  value 
of  these  zones  is  not  local  for  they  have  a  wide  distribution. 

Stonehenge  Member. — The  village  of  Stonehenge,  just  east  of  Cham- 
bersburg,  Pennsylvania,  is  located  on  the  lower  beds  of  the  Beekmantown, 
which  are  sufficiently  distinct  lithologically  and  faunally  from  the  remain- 
ing strata  of  the  formation  to  warrant  their  separation  as  a  distinct 
member.  This  Stonehenge  member  is  composed  of  massive  finely  con- 
glomeratic pure  limestone  in  the  lower  half  and  siliceous  banded  limestone 
alternating  with  layers  of  large  edgewise  conglomerate  in  the  upper  half. 


MARYLAND  GEOLOGICAL  SURVEY 


CAMBRIAN  AND  ORDOVICIAN,  PLATE  XIII 


FlG.  I. — EXPOSURE  OF  STEEPLY  INCLINED  STONEHENGE  LIMESTONE  (UPPER  DIVISION)  AT 
CHARLTON,  MARYLAND,  SHOWING  THE  DISINTEGRATION  INTO  SILICEOUS  SHALE,  UPON  PRO- 
LONGED WEATHERING. 


FlG.  2. — TYPICAL  EXPOSURE  OF  EDGEWISE  CONGLOMERATE  FROM  THE  UPPER  PART  OF  THE 
STONEHENGE  LIMESTONE,  BALTIMORE  AND  OHIO  RAILROAD,  ONE  MILE  NORTH  OF  BALLS,  MARY- 
LAND. 


MARYLAND  GEOLOGICAL  SURVEY  97 

The  lower  Stonehenge  limestone  is  made  up  in  large  part  of  very 
massive  blue  to  dove-colored  limestone  weathering  bluish-white  or 
white.  The  outcrops  are  always  of  a  distinctly  lighter  color  than  the 
associated  formations.  This  feature  is  one  of  several  that  serve  unmis- 
takenly  in  identifying  this  basal  zone  of  the  formation.  On  close  inspec- 
tion a  large  part  of  these  massive  limestone  ledges  appears  to  the  un- 
assisted eye  as  granular  in  texture,  but  under  a  lens  the  granules  prove 
to  be  very  small  brecciated  pieces  of  limestone  usually  less  than  a  sixteenth 
of  an  inch  in  diameter.  These  small  fragments  are  of  a  more  distinctly 
white  color  than  the  surrounding  matrix  and  the  combination  of  a  light 
blue  rock  crowded  with  lighter  colored  minute  angular  fragments  is  very 
distinctive.  The  lower  division  is  further  distinguished  by  absence  of 
chert.  In  all  of  the  numerous  outcrops  that  have  been  studied  no  chert 
of  any  kind  has  been  observed  either  in  the  weathered  limestone  or  in  the 
soil  derived  from  it.  At  intervals  varying  from  an  inch  to  two  inches  the 
limestone  develops  very  thin  layers  of  carbonaceous  or  argillaceous 
material  which  gives  it  a  banded  aspect.  These  layers  or  laminae  are 
usually  about  one-eighth  of  an  inch  in  thickness,  flat  and  parallel  with  the 
bedding  planes.  They  are  quite  unlike  the  sandy  intertwining  laminae  so 
characteristic  of  the  upper  division  of  the  Stonehenge  member. 

Along  the  National  Highway  just  south  of  Funkstown  there  are 
splendid  outcrops  of  typical  lower  Stonehenge  limestone  where  fossils 
may  be  found  and  its  lithologic  character  can  be  studied  to  advantage. 
Hagerstown  and  vicinity  also  affords  numerous,  excellent  and  instructive 
exposures  of  those  beds. 

Excepting  the  shells  of  a  few  brachiopods  the  fossils  in  this  zone  cannot 
be  cleanly  extracted  from  the  rock  because  they  are  so  firmly  cemented 
to  the  fine-grained  matrix  that  in  breaking  the  limestone  with  a  hammer 
the  fracture  passes  through  the  fossils  and  not  along  their  surfaces.  It 
is  only  upon  the  weathered  surfaces  of  the  ledges  that  the  fossils  can  be 
discerned,  and  at  that  merely  as  cross-sections.  The  exposures  near 
Funkstown  have  shown  clearly  that  the  fossils  of  the  lower  Stonehenge 
fauna,  especially  the  cephalopods  and  gastropods  which  constitute  much 


98        THE  CAMBRIAN  AND  ORDOVICIAN  DEPOSITS  OP  MARYLAND 

the  greater  part,  occur  mainly  in  reef-like  masses.  These  reefs  are  of 
slightly  different  material  than  the  enclosing  rock,  lenticular  in  form, 
and  seldom  exceed  two  feet  in  maximum  thickness.  Straight  and  coiled 
cephalopods  are  the  most  abundant  fossils  seen  in  cross-sections  of  these 
reefs,  but  Maclurites  and  Ophil eta-like  gastropods  are  not  uncommon. 

Most  of  the  beds  of  the  upper  Stonehenge  resemble  the  Conococheague 
limestone  so  closely  in  their  development  of  sandy  laminated  strata  with 
numerous  beds  of  edgewise  conglomerate  that  in  areas  of  faulted  or 
intricately  folded  strata  the  distinction  between  the  two  formations  is 
made  with  difficulty.  The  absence  of  chert  in  the  weathered  Stonehenge 
limestone  contrasting  with  its  frequent  occurrence  in  the  Conococheague 
is  perhaps  the  best  of  the  physical  means  of  separation.  It  will  be 
observed  also  that  in  the  upper  Stonehenge  the  sandy  laminae  are  more 
undulating  and  interwoven  than  in  the  laminated  beds  of  the  Conoco- 
cheague in  which  commonly  they  form  relatively  parallel  bands.  The 
•presence  of  shells  of  cephalopods  and  gastropods  in  the  Stonehenge  also 
serves  to  distinguish  this  member  from  the  Conococheague  which  has 
never  yielded  any  molluscan  fossils.  In  areas  where  the  sequence  is 
normal  the  boundary  between  the  two  formations  is  readily  determinate 
by  the  criteria  given.  Desirable  and  conclusive  corroboration  may  be 
secured  by  establishing  the  lower  Beekmantown  sequence  of  ( 1 )  the  lower 
Stonehenge  composed  of  pure  dove-colored  to  gray  strata  containing  beds 
of  a  minute  limestone  conglomerate;  (2)  dark  impure  limestone  with 
undulating  siliceous  laminae  followed  by  (3)  relatively  pure  limestone 
consisting  largely  of  pinkish  marbles. 

All  the  hills  within  the  city  of  Hagerstown  and  its  vicinity  are  formed 
of  the  upper  Stonehenge  limestone,  .and  as  the  quarries  for  building  stone 
in  the  early  days  were  located  on  these  hills,  it  follows  that  many  of  the 
older  buildings  in  Hagerstown  are  of  this  limestone.  The  stone  is  not 
only  easily  quarried  and  dressed,  but  as  it  whitens  in  weathering  and  the 
edgewise  conglomerate  and  wavy  laminae  become  distinctly  visible,  it  has 
also  a  handsome  and  unique  appearance.  Several  of  the  churches  are 
constructed  of  Stonehenge  limestone  and  its  value  and  beauty  as  building 
rock  may  be  seen  particularly  in  St.  John's  Episcopal  Church  on  West 
Antietam  Street,  and  the  Presbyterian  Church  at  the  corner  of  Wash- 


MARYLAND  GEOLOGICAL  SURVEY  :  99 

ington  and  Prospect  streets.  The  conglomeratic  nature  of  the  rock 
is  especially  well  brought  out  in  the  many  stone  embankments  about 
Hagerstown  in  which  long  exposure  to  the  weather  has  emphasized  this 
and  the  laminated  character.  At  the  present  time  brick  and  concrete 
construction  have  largely  displaced  this  limestone  as  building  material. 

Although  the  upper  division  of  the  upper  Stonehenge  is  well  exposed  at 
many  localities  in  Maryland,  perhaps  the  best  places  to  study  it  in  detail 
are  in  the  various  railroad  cuts  around  Hagerstown.  The  cut  on  the 
Western  Maryland  Eailway  one-half  mile  west  of  Bissel  exposes  the 
characteristic  edgewise  conglomerate  and  the  heavy,  wavy  laminae  espe- 
cially well.  At  this  place,  as  well  as  at  other  localities  around  Hagers- 
town, a  few  granular  layers  are  found  crowded  with  brachiopods  and 
poorly  preserved  gastropods. 

Seventeen  species  of  fossils  have  been  noted  in  the  Stonehenge  lime- 
stone of  Maryland  and  Pennsylvania.  Following  Ulrich 1  these  have  been 
correlated  with  the  Tribes  Hill  limestone  fauna  of  New  York.  The  same 
fauna  is  found  also  in  the  upper  part  of  the  Kittatinny  limestone  in  New 
Jersey  and  in  the  basal  or  Stonehenge  limestone  division  of  the  Canadian 
in  central  Pennsylvania.  The  brachipod  Dalmanetta  wemplei  Cleland  is 
found  in  abundance  in  certain  granular  layers,  but  other  fossils  are  not 
so  common.  The  cephalopods  are  almost  confined  to  reef -like  structures 
in  the  purer  limestones  of  the  lower  half.  The  gastropod  Ophileta  com- 
planata  Vanuxem  is  found  in  both  the  lower  and  upper  parts  of  the 
member  and  it  may  be  considered  the  characteristic  fossil. 

Bepresentatives  of  one  species  of  fucoid  and  16  species  of  invertebrates, 
including  one  brachiopod,  six  gastropods,  five  cephalopods,  three  trilo- 
bites,  and  one  branchiopod  crustacean,  have  been  found  in  the  Stonehenge 
member  in  Maryland  sufficiently  well  preserved  for  specific  identification. 
Fragments  of  a  few  more  species  too  imperfect  for  accurate  determination 
have  also  been  noted.  The  gastropod  Ophileta  complanata  is  highly 
characteristic  of  this  part  of  the  Beekmantown  and  the  fauna  may  be 
known  as  the  Ophileta  complanata  fauna.  The  Stonehenge  limestone 

1  Ulrich,  Revision  Paleozoic  Systems.  Bull.  Geol.  Soc.  America,  vol.  xxii, 
1911,  No.  3,  pi.  xxvii;  Ulrich  and  Gushing,  Age  and  Relations  of  the  Little 
Falls  dolomite— N.  Y.  State  Museum,  Bulletin  140,  1910,  p.  137. 


100      THE  CAMBRIAN  AND  ORDOVICIAN  DEPOSITS  OF  MARYLAND 


does  not  leave  any  residual  chert  upon  weathering  and  its  contained 
fossils  unfortunately  do  not  become  silicified.  As  a  result,  their  preserva- 
tion is  not  of  the  best  and  natural  sections  in  the  rock  or  poor  casts  are  the 
rule.  The  granular  beds  associated  with  the  edgewise  conglomerate  of 
the  upper  part  of  the  Stonehenge  limestone  is  the  most  favorable  place 
for  collecting  the  brachiopod  and  gastropod  shells,  some  of  these  beds 
being  fairly  crowded  with  specimens  of  Dalmanella  wemplei.  The 
cephalopods  and  trilobites  have  in  the  main  been  found  in  reef-like 
structures  in  the  lower  Stonehenge  and  their  occurrence  is  therefore  quite 
sporadic.  At  one  point  a  stratum  will  exhibit  numerous  cross-sections 
of  fossils,  but  a  foot  or  two  away  where  the  reef  material  composed  of  a 
very  fine  edgewise  conglomerate  has  disappeared,  no  trace  of  a  fossil  can 
be  found. 

The  following  table  gives  a  list  of  the  Stonehenge  fauna  and  shows  the 
distribution  of  the  species  in  the  Kittatinny  limestone  (upper  part  called 
the  Coplay  limestone)  of  New  Jersey  and  the  Tribes  Hill  limestone  of 
New  York,  formations  with  which  on  strati  graphic  and  paleontologic 
grounds,  the  Stonehenge  is  correlated. 

LIST  OF  STONEHENGE  LIMESTONE  FOSSILS  SHOWING  DISTRIBUTION 


Kittatinny 
lirntstone 
upper  beds) 
of 
New  Jersey 

Tribes  Hill 
limestone 
of 
New  York 

Other  hori- 

ZO  I'S  Of 

Beekmaii- 
to\vn 

Stonehenge 
limestone 
of  Pennsyl- 
vania and 
Maryland 

Pdlcrophycus  tubulare  Hall  

* 

* 

Ddlinunello  wemplei  C  leland  

* 

* 

* 

Ophileta  complanata  Vanuxem  

* 

* 

Ophileta  levata  Vanuxem  .  

* 

* 

Eccyliomphalus  multiseptarius  Cleland.  .  . 
Plcurotomaria  ??  floridensis  Cleland  
Raphistoma  f  obtunum  Cleland  

* 
* 
* 

* 
# 
* 

Raphistoma  f  columbianum  Weller  

* 

* 

Orthoccras  primigenium  Hall  

* 

* 

* 

Ooceras  kirbyi  Wh  itfield  

* 

* 

* 

CyrtoceTas  qracile  Cloland  

* 

# 

# 

Cyrtoceras  beekmanense  Vv  bitfield  
Cyclostomiceras  cassinensef   (Wh  itfield).. 
Asaphell.us  gyracanthus  Raymond  

* 

* 

* 
* 

* 
* 
* 

Hemigyraspis  collieana  Raymond  

* 

SymphyfsuTiift  convexus  (Cleland)  

* 

* 

* 

Ribeiria  nuciilitiformis  Cleland  

* 

* 

MARYLAND  GEOLOGICAL  SURVEY 


CAMBRIAN  AND  ORDOVICIAN,  PLATE  XIV 


no.  1. — VIEW  OF  A  WEATHERED  OUTCROP  OF  THE  UPPER  STONEHENGE  LIMESTONE,  EASTERN 
EDGE  OF  HAGERSTOWN,  MARYLAND. 


2. VIEW   TAKEN   FROM   HILL  OF  UPPER   STONEHENGE  LIMESTONE,  EASTERN   EDGE  OF 

HAGERSTOWN,  MARYLAND,  LOOKING  EAST,  SHOWING  EFFECT  OF  WEATHERING  OF  THE 
VARIOUS  FORMATIONS  UPON  TOPOGRAPHY.  THE  VALLEY  IN  THE  FOREGROUND  IS  IN  THE 
LOWER  STONEHENGE  PURE  LIMESTONE  WHILE  THE  RIDGE  IS  FORMED  OF  THE  SILICEOUS,  MORE 
RESISTANT  UPPER  STONEHENGE.  SOUTH  MOUNTAIN  IS  SEEN  IN  THE  DISTANCE. 


MARYLAND  GEOLOGICAL  SURVEY  101 

In  Maryland  and  southern  Pennsylvania,  the  Beekmantown  strata  fol- 
lowing the  Stonehenge  member  are  so  uniform  in  lithologic  character 
that  their  separation  into  distinct  formations  is  impracticable.  In  the 
Nittanny  and  other  valleys  in  central  Pennsylvania  the  corresponding 
strata  not  only  attain  a  much  greater  thickness,  but  also  are  so  developed 
that  four  formations  are  readily  distinguishable.  These  are,  in  ascending 
order,  (1)  the  Stonehenge  limestone  at  the  base  with  a  thickness  of 
662  feet;  (2)  the  Nittanny  dolomite,  1267  feet  thick,  cherty  and  holding 
the  Cryptozoon  steeli  fauna  in  its  lower  part;  (3)  the  Axeman  limestone 
158  feet,  and  (4)  the  Bellefonte  dolomite  2145  feet  thick.  The  entire 
series,  with  both  overlying  and  underlying  formations,  is  to  be  seen  in 
excellent  and  practically  continuous  exposures  at  Bellefonte,  Pennsyl- 
vania. As  this  section  gives  the  maximum  known  development  of  the 
Canadian  system  in  the  Appalachians,  the  four  formations  into  which  it 
has  been  divided  as  above  by  Ulrich  have  been  adopted  in  the  general 
time  scale. 

Cryptozoon  steeli  Zone. — Following  the  Stonehenge  member,  which  has 
just  been  described,  are  600  or  more  feet  of  cherty  oolitic  limestones,  dove- 
colored,  fine-grained  pure  limestone  and  usually  dense  textured  pink 
marble.  The  basal  60  feet  consisting  mainly  of  oolitic  cherty  limestone 
contains  the  characteristic  fossil  of  this  division — a  globular  mass,  com- 
monly four  to  eight  inches  in  diameter  composed  of  concentric  layers 
and  supposed  to  represent  the  secretion  of  calcareous  algae  to  which  the 
name  Cryptozoon  steeli  has  been  applied.  Though  doubtless  calcareous 
originally,  these  rounded  masses  are  now  almost  without  exception  more 
or  less  completely  replaced  by  silica  in  the'  form  of  chert.  This  fossil 
occupies  a  similar  position  in  the  Beekmantown  throughout  the  Appa- 
lachian Valley  and  it  is  so  abundant  and  characteristic  that  this  division 
is  termed  the  Cryptozoon  steeli  zone.  Subaerial  decomposition  of  these 
particular  strata  leaves  a  light  reddish  residual  clay  and  soil  containing 
an  abundance  of  ordinary  yellow  "platy  chert  besides  the  numerous  rounded 
silicified  masses  of  Cryptozoon.  These  cherty  residual  masses  unfailingly 
identify  the  outcrop  of  this  zone.  It  is  particularly  well  exposed  in  the 


102      THE  CAMBRIAN  AND  ORDOVICIAN  DEPOSITS  OF  MARYLAND 

railroad  cut  about  three-fourths  of  a  mile  east  of  Charlton,  Md.  Here 
deep  weathering  and  decomposition  of  the  steeply  dipping  limestone  strata 
has  removed  their  calcareous  matter  and  left  only  residual  clays  with 
the  chert  clearly  marking  its  position.  The  abundance  of  chert  and 
silicified  Cryptozoon  heads  formed  in  the  weathering  of  this  zone  is  well 
attested  by  the  frequent  piles  of  chert  collected  along  the  roadways. 

Immediately  following  this  cherty  zone  with  Cryptozoon  are  300  feet 
of  dove  and  pink  fine-grained  pure  limestone,  of  which  a  considerable 
portion  can  be  called  marble.  These  marble  beds  are  well  shown  in  several 
railroad  cuts  around  Hagerstown.  Fossils  are  rare  in  these  strata,  but  an 
occasional  layer  shows  traces  of  species  found  also  in  the  underlying  beds 
holding  Cryptozoon  steeli.  This  zone  ends  with  275  feet  of  fine-grained, 
nearly  pure  limestone  with  occasional  beds  of  magnesian  limestone  and 
several  layers  of  porous  chert. 

The  platy  chert,  weathering  out  of  the  limestone  of  the  Cryptozoon  steeli 
zone  is  common  at  all  outcrops  of  the  zone,  but  is  so  abundant  in  the 
western  half  of  the  valley  that  it  occasions  a  distinct  row  of  hills  marking 
the  line  of  outcrop.  This  topographic  feature  and  the  numerous  masses 
of  Cryptozoon  associated  with  the  chert  cause  this  portion  of  the  Beekman- 
town  to  be  easily  recognized.  The  following  species  have  been  found  either 
associated  with  Cryptozoon  steeli  or  in  strata  underlying  it,  but  still 
included  in  this  division  : 

Fossils  of  Cryptozoon  steeli  Zone 

Cryptozoon  steeli  Seely 
Rhabdaria  fragilis  (Billings) 
Tetradium  simplex  new  species 
Syntrophia  lateralis  (Whitfield) 
Maclurites  affinis  (Billings) 
Eccyliopterus  triangulus  (Whitfield) 
Ophileta  compacta  Salter 
Hystricurus  conicus  (Billings) 

At  the  very  base  of  this  zone  two  interesting  fossils  have  been  found 
associated  with  the  usual  gastropods.  These  are  the  sponge-like  organism 
Rhabdaria  fragilis  Billings  and  Tetradium  simplex,  a  new  species  of  coral 
of  particular  interest  in  being  the  oldest  known  undoubted  coral. 


MARYLAND  GEOLOGICAL  SURVEY  103 

The  Maryland  outcrops  of  the  Cryptozoon  steeli  zone  are  so  numerous 
and  easily  located  both  on  the  map  and  in  the  field  that  only  a  few  locali- 
ties need  be  mentioned.  In  the  western  half  of  the  valley,  outcrops  along 
the  Western  Maryland  Railway,  especially  three-quarters  of  a  mile  east 
of  Charlton,  show  these  rocks  and  their  contained  fossils.  East  of  the 
Martinsburg  shale  belt,  exposures  in  the  vicinity  of  Williamsport  and 
also  north  and  west  of  Hagerstown  have  afforded  fossils.  In  the  western 
part  of  the  valley  the  line  of  hills  in  the  Beekmantown  area  next  to  the 
Beekmantown-Conococheague  boundary  represents  this  zone,  but  in  the 
eastern  part  the  exposures  parallel  a  line  of  hills  caused  by  the  more 
resistant  Stonehenge  beds. 

Ceratopea  Zone. — Succeeding  the  dove  and  pink  pure  limestones  and 
marbles  of  the  Cryptozoon  steeli  zone  are  250  feet  of  blue  and  dove  lime- 
stone cherty  in  the  upper  half,  containing  horn-like  fossils  known  by  the 
generic  name  Ceratopea.  The  exact  nature  of  these  fossils  is  unknown, 
but  they  are  believed  to  be  the  opercula  of  large  gastropods  like  Maclu- 
rites.  From  a  stratigraphic  standpoint  they  are  of  considerable  interest 
because  this  particular  species  and  the  fauna  associated  with  it  has  a  wide 
geographic  distribution,  but  restricted  geologic  range  throughout  the 
Appalachian  and  Mississippi  valleys.  Free  silicified  specimens  of  this 
organism  occur  in  the  soil  where  this  zone  outcrops,  or  they  may  be  found 
attached  to  the  limestone.  Associated  with  the  Ceratopea  are  a  few 
species  of  gastropods  and  fragments  of  trilobites,  but  the  Ceratopea  itself 
is  the  most  characteristic  fossil  of  the  division.  In  Maryland  numerous 
outcrops  of  this  zone  can  be  found  in  the  vicinity  of  Halfway,  particularly 
in  cuts  along  the  Cumberland  Valley  Railroad.  Localities  near  Hagers- 
town have  also  afforded  this  fossil,  although  in  no  place  has  it  been  found 
in  the  abundance  that  prevails  in  Virginia  and  the  states  to  the  south. 

The  fauna  of  the  Ceratopea  zone  so  far  identified  consists  of  nine 
species.  Fragments  of  a  few  other  species  have  been  noted,  but  they  are 
too  imperfect  for  description  and  can  only  be  identified  with  certainty 
when  a  monographic  study  of  the  entire  Beekmantown  formation  has 
been  made. 


104      THE  CAMBRIAN  AND  ORDOVICIAN  DEPOSITS  OF  MARYLAND 

Fossils  of  the  Ceratopea  Zone 

Dalmanella  electro,  (Billings) 
Pleurotomaria  ff  canadensis  Billings 
Hormotoma  artemesia  (Billings) 
Maclurites  sordidus  (Hall) 
Ceratopea  keithi  Ulrich 
Raphistomina  laurentina  (Billings) 
Goniurus  caudatus  (Billings) 
Pliomerops  salteri  (Billings) 
Isochilina  gregaria  (Whitfield) 

Turritoma  Zone. — The  next  division  of  the  Beekmantown  consists  of 
about  575  feet  of  pure  dove  and  gray  laminated  magnesian  limestone, 
which  contains  in  its  upper  part  high-spired  gastropods  with  a  species 
of  Turritoma  apparently  confined  to  these  beds.  The  lower  375  feet  of 
the  Turritoma  zone  is  composed  of  alternating  highly  magnesian,  finely 
laminated  gray  limestones  and  pure  gray  and  pure  clove  limestone  with 
occasional  beds  or  streaks  of  fine  limestone  conglomerate.  The  basal  75 
feet' of  this  portion  occasionally  exhibits  a  few  fossils  of  which  Syntrophia 
lateralis  and  species  of  Maclurites  and  Liospira  are  most  often  found. 

The  association  of  species  called  the  Turritoma  fauna  is  found  only  in 
the  upper  200  feet  of  this  division  where  the  fossils  usually  occur  in  beds 
that  weather  so  as  to  appear  riddled  with  worm  borings!  Here  the  fossils 
are  not  silicified,  but  they  occur  as  dolomitic  casts,  often,  however,  in 
good  preservation.  They  are  extremely  fragile  and  much  care  is  required 
to  preserve  them.  Gastropods,  particularly  the  species  Turritoma  acrea 
(Billings),  are  most  conspicuous.  A  number  of  species  of  fossils,  too 
imperfectly  preserved  for  recognition,  occur  in  this  zone  in  Maryland; 
eight  species  have  been  identified  specifically.  The  strata  with  Turritoma 
are  the  uppermost  fossiliferous  rocks  of  the  Beekmantown,  but  they  are 
followed  by  400  feet  of  finely  laminated,  gray,  interbedded  pure  and 
magnesian  limestone  of  the  type  considered  characteristic  of  the  forma- 
tion as  a  whole.  At  the  top  of  these  finely  laminated  beds  are  sandy  cherts 
and  hard,  dense  white  chert  marking  the  top  of  the  Beekmantown.  Asso- 
ciated with  these  cherts  and  continuing  upward  for  about  40  feet  are 
great  numbers  of  the  secondarily  silicified  cherts  which  have  assumed 


MARYLAND  GEOLOGICAL  SURVEY 


CAMBRIAN  AND  ORDOVICIAN,  PLATE  XV 


FlG.  I. — EXPOSURE  OF  LOWER  BEEKMANTOWN  LIMESTONE  JUST  ABOVE  THE  STONEHENGE 
MEMBER  IN  BRICKYARD,  EASTERN  EDGE  OF  HAGERSTOWN,  MARYLAND.  CLAY  FOR  BRICK 
MANUFACTURE  RESULTS  FROM  THE  WEATHERING  OF  THE  PURER  BEDS. 


FlG.  2. — BEEKMANTOWN  LIMESTONE  AT  LEGORE  QUARRY,  LEGORE,  MARYLAND.     THE  WEATHERED 
OUTCROPS   OF   THESE    STRATA    HAVE   YIELDED   NUMEROUS    CEPHALOPODS. 


MARYLAND  GEOLOGICAL  SUKVEY  105 

the  form  of  a  cauliflower.  These  mark  the  boundary  between  the  Beek- 
mantown and  Stones  River  limestones.  As  explained  on  another  page, 
the  secondary  silicification  necessary  to  form  the  cauliflower  variety  is 
supposed  to  have  occurred  in  the  time  interval  between  the  two  formations 
when  the  Beekmantown  rocks  formed  a  land  area. 

Sometimes  the  upper  Beekmantown  strata  holding  the  Turritoma 
fauna  do  not  weather  as  described  above,  but  show  the  usual  occurrence  of 
smooth,  rounded  outcrops  in  which  the  fossils,  although  numerous,  appear 
only  as  natural  sections  in  the  rock.  Such  exposures  along  the  National 
Highway  in  the  vicinity  of  Huyett,  Maryland,  have  yielded  the  following 
species : 

Fossils  of  the  Turritoma  Zone  in  Maryland 

Dalmanella  electro,  (Billings) 
Pleurotomaria  ??  gregaria,  Billings 
Hormotoma  gracilens  (Whitfield) 
Turritoma  acrea  (Billings) 
Maclurites  oceanus  (Billings) 
Eccyliopterus  disjunctus  .(Billings) 
Cyrtocerina  mercurius  Billings 
Trocholites  internistriatus    (Whitfield) 
Isochilina  seelyi  (Whitfield) 

Traces  of  this  fauna,  although  always  in  poor  preservation,  have  been 
noted  at  numerous  places  in  Maryland,  in  fact  Beekmantown  strata 
exposed  near  the  boundary  line  of  the  Stones  Eiver  areas  usually  reveal 
one  or  more  layers  showing  natural  sections  of  these  fossils. 

TOPOGRAPHY  AXD  RESIDUAL  PRODUCTS. — The  Beekmantown  as  a  whole 
produces  gently  rolling  country,  but  the  lower  Stonehenge  member  and 
a  zone  about  800  feet  above  the  base  of  the  formation  give  rise  to  very 
characteristic  topographic  features,  which  are  of  extreme  importance  ill 
the  mapping  of  areas  in  which  rock  outcrops  are  infrequent. 

These  topographic  features  are  the  result  of  the  various  siliceous 
products  left  in  the  soil  by  weathering  of  the  limestone.  They  are  so 
distinctive  that  they  become  as  important  factors  in  the  identification 
of  the  strata  as  the  .characters  of  the  rock  itself  or  of  its  contained 
fossils.  In  the  absence  of  fossil  remains  or  indeed  of  satisfactory  rock 


106      THE  CAMBRIAN  AND  ORDOVICIAN  DEPOSITS  OF  MARYLAND 

outcrops  it  is  often  possible  to  determine  the  underground  stratigraphy 
by  the  character  of  these  surface  residual  products  alone.  In  fact  such 
criteria  were  alone  available  over  considerable  stretches  of  the  rolling 
agricultural  country  with  few  rock  exposures,  that  in  this  region  at  least, 
is  characteristic  of  Beekmantown  limestone  areas.  On  this  account, 
although  they  have  been  mentioned  incidentally  and  repeatedly  in  fore- 
going pages,  it  seems  desirable  to  give  here  a  connected  discussion  of  the 
three  most  important  residual  products,  namely,  the  siliceous  shale  frag- 
ments near  the  base  of  the  formation,  Cryptozoon  and  platy  yellow  chert 
near  the  middle,  and  the  cauliflower  chert  at  the  top. 

The  relatively  pure  limestone  of  the  lower  half  of  the  Stonehenge 
member  weathers  rapidly  and  as  its  surface  is  not  held  up  by  some 
resistant  residual  a  slight  depression  in  the  land  surface  results.  On 
the  other  hand,  the  upper  half  of  the  Stonehenge  member,  with  its  sandy 
laminated  strata  weathering  into  a  protective  covering  of  thin  siliceous 
shale  fragments,  forms  hills  corresponding  in  width  to  the  outcrops  and 
trending  in  the  direction  of  the  strike  of  its  beds.  As  the  Beekmantown 
everywhere  in  the  Appalachian  Valley  of  Maryland  is  highly  folded,  these 
hills  assume  the  usual  northeast-southwest  direction  of  the  folds  and 
their  development  is  so  marked  a  feature  that  by  plotting  these  elongated 
narrow  hills,  the  upper  Stonehenge  member  can  be  mapped  in  areas  of 
few  outcrops  of  the  rock  itself.  When  the  succession  is  normal  the  lower 
Stonehenge  limestone  therefore  occurs  in  a  slight  valley  between  the  low 
hills  of  the  upper  Stonehenge  on  one  side  and  the  higher  land  on  the  other 
side  formed  by  the  chert  weathered  out  of  the  upper  part  of  the  Conoco- 
cheague  limestone.  This  topographic  feature,  however,  is  well  developed 
only  to  the  east  of  the  Martinsburg  shale  belt.  West  of  this  belt  the 
siliceous  content  of  the  laminated  division  of  the  Stonehenge  is  so  much 
less  that  it  has  little  effect  on  the  topography.  This  topographic  feature 
of  the  Stonehenge  in  connection  with  the  line  of  hills  next  described 
makes  it  possible  to  map  the  complicated  folds  involving  the  Beekman 
town  limestone  without  much  doubt  and  has  greatly  aided  in  deciphering 
the  geologic  structure  in  areas  of  few  outcrops.  The  Beekmantown  rocks 
next  or  immediately  succeeding  following  the  Stonehenge  divisions  are 


MARYLAND  GEOLOGICAL  SURVEY  107 

of  a  more  soluble  nature  and  therefore  weather  into  lowland  areas  again. 
Therefore  the  broad  area  of  folded  Beekmantown  limestones  in  which 
Hagerstown  is  located  presents  a  succession  of  elongated  highland  areas 
alternating  with  usually  broader  lowland  areas.  This  alternation  in  the 
topography  is  well  shown  in  Hagerstown  itself,  where  the  hills  passing 
through  the  town  are  composed  of  upper  Stonehenge  limestone  and  the 
low  areas  between  them  are  underlaid  by  lower  Stonehenge  or  by  the  over- 
lying Beekmantown  limestone. 

The  line  of  low  hills  formed  by  the  upper  member  of  the  Stonehenge 
limestone  is  a  characteristic  feature  of  the  Beekmantown  topography 
only,  as  noted  before,  in  the  eastern  half  of  the  Appalachian  Valley  of 
Maryland,  because  west  of  the  Martinsburg  shale  belt  the  siliceous  nature 
of  this  -member  is  not  so  well  developed  and  consequently  weathers  much 
like  the  remaining  portions  of  the  Beekmantown.  The  marked  topo- 
graphic feature  of  the  western  belt  of  outcrops  is  a  line  of  hills  composed 
of  the  chert  derived  from  the  Cryptozoon  steeli  zone  of  the  formation 
which  is  unusually  well  developed  in  this  part  of  the  Valley.  Here  speci- 
mens of  the  Cryptozoon  are  very  abundant,  and  as  they  silicify  upon 
weathering,  their  remains  leave  considerable  masses  of  chert  in  the  soil 
However,  the  greater  part  of  this  residual  material  consists  of  yellow, 
platy,  flinty  chert  formed  by  replacement  of  certain  layers  of  the  lime- 
stone. The  Beekmantown  limestone  weathers  so  readily  that  the  deter- 
mination of  the  geologic  structure  of  the  formation  in  many  cases  would 
be  almost  impossible  were  it  not  for  this  extensive  development  of  Crypto- 
zoon and  its  accompanying  chert.  This  chert  zone  is  plotted  on  the  map 
of  the  western  part  of  the  Valley  where  it  gives  a  clue  to  the  lower 
boundary  of  the  formation  and  also  aids  in  determining  the  structure. 
For  example,  the  small  synclinal  area  on  the  west  flank  of  the  larger 
synclinal  area  three  miles  northeast  of  Clear  Spring  is  an  interesting 
case  of  this  zone's  value  in  determining  structural  relations. 

The  cauliflower  chert  developed  at  the  top  of  the  Beekmantown  does 
not  occur  abundantly  enough  or  through  a  sufficient  thickness  of  strata 
to  form  a  topographic  feature,  but  the  unusual  shape  of  these  flinty 
objects  is  so  characteristic  that  their  presence  in  the  soil  is  the  surest 


108      THE  CAMBRIAN  AND  ORDOVICIAN  DEPOSITS  OF  MARYLAND 

criterion  in  determining  the  dividing  line  between  the  Beekmantown 
and  the  overlying  Stones  River  limestone.  These  cherts  are  believed  by 
some  students  to  represent  in  reality  the  physical  evidence  of  the  uncon- 
formity between  these  two  great  limestone  formations.  Unlike  many 
other  cherts  they  are  not  the  result  of  present-day  surface  weathering,  but 
appear  to  have  been  formed  in  the  land  interval  between  the  two  forma- 
tions. These  cherts  occur  as  a  regular  bedded  deposit  and  their  origin 
seems  to  be  as  follows : 

With  the  uplift  at  the  end  of  Beekmantown  time,  weathering  of  the 
exposed  limestones  took  place,  resulting,  as  it  does  to-day,  under  favorable 
conditions,  in  a  soil  with  more  or  less  numerous  chert  fragments.  Con- 
tinual exposure  to  waters  bearing  silica  in  solution  caused  a  secondary 
silicification  of  these  cherts  by  the  formation  of  rosettes  of  silica  over 
their  surface.  The  rosette  areas  continued  to  grow  larger  and  larger 
until  the  characteristic  cauliflower  shape  resulted.  The  reason  for  the 
formation  of  such  rosettes  is  obscure,  but  it  is  a  fact  that  fractured  fossils 
or  pieces  of  chert  will  develop  areas  of  rosette  quartz  along  the  fractured 
zones  if  subjected  to  the  influence  of  silica-bearing  waters.  All  of  the 
chert  at  the  top  of  the  Beekmantown  has  not  undergone  secondary  silici- 
fication into  the  cauliflower  form.  Fragments  of  platy  chert  representing 
the  primary  silicification  stage  may  occasionally  be  noted  with  fracture 
zones  penetrating  into  or  entirely  through  them.  The  water  with  silica 
in  solution  will  seep  into  these  fractures  and  deposit  the  silica  there  first, 
thus  starting  a  growth  area  which  develops  into  the  characteristic  rosettes 
of  the  cauliflower  variety.  By  this  process  a  small  fragment  of  platy  or 
irregular  chert  by  continual  growth  of  the  rosette  areas  will  develop  into 
specimens  of  the  cauliflower  variety  a  foot  or  more  in  diameter. 

Apparently  the  same  process  occurs  in  fractured  fossils  found  in  cer- 
tain siliceous  shale  formations,  particularly  of  Silurian  and  Missis- 
sippian  ages.  For  example,  a  crinoid  column  of  say  one-half  inch  in 
diameter,  exposed  to  silic'a-bearing  waters,  will  first  receive  a  deposit  of 
silica  in  its  central  canal  and  rosettes  of  silica  will  project  from  each  end. 
The  column  is  fractured  by  this  process  and  each  fracture  line  then 


MARYLAND  GEOLOGICAL  SURVEY 


CAMBRIAN  AND  ORDOVICIAN,  PLATE  XVI 


FlG.    I. — NEAR  VIEW  OF  BEEKMANTOWN  LIMESTONE  AT  LEGORE  QUARRY,  LEGORE,   MARYLAND. 
STRATA  PENETRATED  BY  A  SIX-INCH   DIABASE  DYKE    (MARKED  BY   HAMMER). 


FlG.  2. — VIEW  OF  CONTACT  BETWEEN  THE  BEEKMANTOWN  (B)  AND  STONES  RIVER  (s) 
LIMESTONES  ALONG  THE  SOUTH  SIDE  OF  THE  NATIONAL  HIGHWAY  AT  WILSON,  MARYLAND. 
THE  ZONE  OF  CAULIFLOWER  CHERT  (c)  IS  WELL  DISPLAYED  AT  THIS  PLACE. 


MARYLAND  GEOLOGICAL  SURVEY  109 

becomes  filled  with  silica  which,  with  continual  deposition,  enlarges  the 
original  small  column  into  a  mass  several  inches  in  diameter.  Usually 
in  such  cases  the  resulting  mass  is  hollow  and  lined  internally  with 
crystals,  thus  forming  a  geode.  Sometimes,  however,  it  is  solid,  in  which 
event  a  structure  not  unlike  the  cauliflower  chert  results. 

The  general  problem  of  silicification  is  most  complicated  and  little  is 
known  yet  of  either  its  chemical  or  physical  aspects.  Why  a  certain 
limestone  should,  under  past  or  present-day  weathering,  develop  chert 
products  which  are  so  alike  over  large  areas  that  they  can  be  used  in  the 
determination  of  the  bed,  is  not  only  an  interesting  question  scientifically, 
but  it  is  also  of  such  geological  importance  as  to  merit  the  most  detailed 
study. 

Another  interesting  feature  in  connection  with  the  cauliflower  chert  is 
its  occurrence,  noted  at  several  places,  in  a  black  shale,  sometimes  regu- 
larly bedded  but  again  irregularly  deposited,  much  resembling  an  ancient 
soil.  Such  a  shale  bed  at  the  top  of  the  Beekmantown  may  be  seen  in  the 
cut  along  the  National  Highway  just  west  of  Wilson,  Md.  Cauliflower 
cherts  are  very  abundant  in  this  shale  bed  and  its  surface  outcrop  strews 
the  ground  with  the  irregular  masses.  However,  they  are  not  limited 
to  this  shale,  for  here,  as  well  as  at  other  places,  the  typical  chert  occurs 
in  regularly  bedded  dolomite. 

Although  discussed  here  in  connection  with  the  Beekmantown,  the  zone 
of  cauliflower  chert,  if  the  above  explanation  is  correct,  should  be  regarded 
as  basal  Stones  River.  It  might  in  reality  be  regarded  as  a  basal  con- 
glomerate formed,  however,  in  a  totally  different  manner  from  other 
conglomerates. 

AREAL  DISTRIBUTION. — The  Beekmantown  limestone  with  its  basal 
Stonehenge  member  is  the  most  widely  distributed  early  Paleozoic  forma- 
tion in  Maryland,  as  its  outcrop  covers  large  areas  in  both  the  Appalachian 
and  Frederick  valleys  where  its  strata  weather  rapidly  into  good  soil  and 
produce  a  gently  rolling  country  with  excellent  farm  land. 

In  the  eastern  belt  of  outcrop  in  the  Appalachian  Valley  the  formation 
is  closely  folded,  occupying  an  area  equal  to  half  that  of  the  Valley  and 

7 


110      THE  CAMBRIAN  AND  ORDOVICIAN  DEPOSITS  OF  MARYLAND 

extending  from  a  line  passing  through  Security,  three  miles  east  of 
Hagerstown,  to  a  northeast-southwest  line  west  of  Williamsport  where  a 
fault  brings  the  limestone  in  contact  with  the  Martinsburg  shale.  The 
broad  expanse  of  Conococheague  limestone  in  southern  Maryland  reduces 
•the  width  of  the  Beekmantown  here  from  a  belt  almost  seven  miles  wide 
at  the  Pennsylvania  state  line  to  less  than  three  at  the  Potomac.  South 
of  Hagerstown  the  Conococheague  and  Beekmantown  limestones  are 
intimately  folded  together,  exhibiting  characteristic  Appalachian  pitch- 
ing anticlines  and  synclines.  The  western  edge  of  this  belt  is  a  fault  line 
except  at  the  extreme  northern  and  southern  ends  where  the  normal 
sequence  is  resumed.  This  fault  is  clearly  shown  at  Williamsport  where 
the  middle  limestone  of  the  Beekmantown  may  be  seen  in  contact  with 
the  lower  Martinsburg  shale.  North  of  Williamsport  the  displacement 
of  this  fault  is  greater  and  brings  the  Beekmantown  in  contact  with  the 
upper  sandy  portion  of  the  Martinsburg.  Infolded  in  this  large  area  01 
Beekmantown  are  elongated,  narrow  bands  of  the  purer  limestones  of  the 
succeeding  Stones  Eiver  formation. 

In  the  area  west  of  the  Martinsburg  shale  plateau  the  Beekmantown 
limestone  likewise  occupies  about  one-half  of  this  part  of  the  Appalachian 
Valley,  but  here  closely  folding  with  the  Conococheague  limestone  causes 
each  formation  to  appear  at  the  surface  in  elongated,  more  or  less  parallel 
bands.  The  continuity  of  these  bands  is  broken  in  the  northern  part  of 
the  state  by  a  transverse  fault.  West  of  the  eastern  base  of  North 
Mountain  no  rocks  of  Beekmantown  age  are  exposed. 

The  surface  rock  of  a  considerable  portion  of  the  Frederick  Valley 
belongs  to  the  red  beds  of  Triassic  age,  but  of  the  limestone  portion  of 
the  valley  about  one-half  is  occupied  by  strata  referred  to  the  Beekman- 
town. These  Beekmantown  areas  occupy  in  general  the  eastern  half  of 
this  portion,  although  folding  brings  small  areas  to  the  surface  in  the 
western  half.  Two  small  areas  just  east  of  Catoctin  Mountain  are  of 
interest  because  erosion  of  the  red  beds  has  proceeded  far  enough  to 
expose  the  underlying  Beekmantown  strata. 


MARYLAND  GEOLOGICAL  SURVEY  111 

East  of  the  Frederick  Valley  on  the  Piedmont  Plateau,  narrow,  elon- 
gated, infolded  areas  of  limestone  occur,  only  one  of  which  is  shown  on 
the  map  because  of  its  evident  relationship  to  the  limestone  of  the  valley 
proper.  Metamorphism  has  destroyed  the  evidence  as  to  the  age  rela- 
tions of  these  limestones,  although  it  is  possible  that  they  represent  an 
eastern  extension  of  the  f  ossilif  erous  Beekmantown  strata  .of  the  Frederick 
Valley. 

FREDERICK  VALLEY  LIMESTONES 

The  considerable  development  of  Early  Paleozoic  limestones  east  of 
Catoctin  Mountain  in  the  Frederick  Valley  and  their  economic  value  has 
long  been  known  to  geologists.  As  these  deposits  occur  east  of  the  Blue 
Ridge  and  are  the  easternmost  unmetamorphosed  Paleozoic  strata  known, 
the  determination  of  their  exact  age  relations  is  a  matter  of  importance 
and  interest.  The  Frederick  Valley  is  bounded  on  the  west  by  Catoctin 
Mountain,  composed  of  Lower  Cambrian  sandstone  and  shale,  and  on  the 
east  by  a  range  of  low  hills  formed  by  pre-Cambrian  schist.  The  length 
of  the  limestone  area  is  about  30  miles  and  its  maximum  breadth  about 
six  miles.  North  of  LeGore,  Maryland,  the  limestones  pass  under  cover 
of  the  Newark  red  beds,  while  at  the  Potomac  they  cross  into  Virginia 
where  they  again  soon  disappear  under  the  red  beds. 

This  area  has  been  studied  by  several  geologists,  but  the  most  important 
work  upon  it  was  that  of  Keyes,  who  published  his  results  in  1890  in  the 
Johns  Hopkins  University  Circular.  His  description  of  these  rocks  is 
as  follows :  "  The  beds  have  a  mean  dip  of  about  25  degrees  to  the  east- 
ward. Along  their  western  border  they  are  covered  by  Triassic  red  sand- 
stones (Newark  formation).  To  the  east  the  limestones  pass  gradually 
into  shales  and  slates,  the  whole  forming  apparently  a  conformable  series. 
The  limestones  in  great  part  are  bluish  in  color,  compact  and  heavily 
bedded ;  but  on  approaching  the  shales  they  become  more  and  more  thinly 
bedded  and  very  dark  blue  or  nearly  black,  owing  to  the  bituminous 
matter  present.  The  latter,  however,  is  driven  off  by  burning,  leaving  a 
pure  white  lime.  In  places  this  lime  rock  is  highly  siliceous  on  account 
of  the  presence  of  a  considerable  amount  of  rather  coarse  quartz  sand. 

8 


C 


I) 


112      THE  CAMBRIAN  AND  ORDOVICIAN  DEPOSITS  OF  MARYLAND 

This  large  amount  of  silica  renders  the  rock  unfit  for  the  manufacture 
of  lime,  which  at  present  is  the  chief  use  to  which  the  Frederick  Valley 
limestones  are  put.  From  the  thin-bedded  belt  the  limestone  passes  into 
a  more  earthy  facies  and  grades  into  dark  colored  calcareous  shales  and 
these  again  into  slates  or  into  sandy  shales." 


7T, 


FlG.    12. STRUCTURE    SECTIONS    ACROSS    FREDERICK    VALLEY. 


A.  Devilbiss  Bridge  east  through  McAleer. 

B.  Braddock  Heights  east  through  Frederick. 


C.  East-west    section    through    Frederick    Junction. 

D.  East-west  section  through  Buckeystown. 


Tn — Newark  sandstone  and  shale. 
Tnc — Newark  conglomerate. 
Ob — Beekmantown  limestone. 


SYMBOLS. 

Of — Frederick  limestone. 

Ch — Harpers  shale. 

Cw — Weverton  sandstone. 


Ol — Loudon  formation, 
Ac — Catoctin  schist. 


Keyes  found  a  few  species  of  fossils  in  these  limestones  which  led  him 
to  suggest  that  the  whole  series  was  equivalent  to  the  Chazy,  Trenton, 
and  Hudson  River  formations.  The  determination  of  the  age  and 
structure  relations  of  the  Frederick  Valley  limestones  was  a  matter  of 


MARYLAND  GEOLOGICAL  SURVEY  113 

some  difficulty,  and  the  present  author  was  fortunate  in  having  this  earlier 
work  upon  the  subject  even  though  he  is  unable  to  agree  with  some  of  the 
conclusions.  Comparison  of  the  four  structure  sections  across  the 
Frederick  Valley,  here  presented  as  fig.  12  with  that  published  by  Keyes, 
will  show  that  the  present  conception  of  the  structure  and  stratigraphy 
differs  radically. 

The  lowest  sedimentary  rocks  of  this  particular  region  are  comprised  in 
the  Lower  Cambrian  quartzites,  the  Weverton  sandstone  and  the  succeed- 
ing Lower  Cambrian  Harpers  shale  exposed  in  Catoctin  Mountain.  Sugar 
Loaf  Mountain,  on  the  east,  likewise  is  composed  of  Lower  Cambrian 
quartzite.  In  the  opinion  of  the  writer  the  limestone  series  does  not  pass 
upward  on  the  eastern  side  of  the  valley  into  Hudson  River  shales,  but  it 
is  faulted  against  shales  and  schists  which  are  of  pre-Cambrian  age. 
Along  the  western  side  of  the  Frederick  Valley  the  limestones  are  covered 
by  the  conglomerate,  red  sandstone  and  shale  of  the  Newark  series  except 
in  two  areas  where  stream  erosion  has  cut  deeply  into  and  in  places  almost 
to  the  base  of  the  underlying  limestones. 

The  structural  relations  of  the  Frederick  Valley  are  so  complicated  that 
it  would  be  difficult  to  unravel  the  stratigraphy  were  it  not  for  the  occa- 
sional presence  of  fossils.  Determinable,  though  but  rarely  preserved, 
fossil  remains  have  been  noted  at  numerous  places  in  the  valley  in  two 
distinct  kinds  of  rocks,  namely,  in  dark  blue  thin-bedded  strata,  known 
locally  as  the  building  rock,  and  in  massive,  rather  pure,  blue  to  white 
limestone  that  is  quarried  for  lime.  The  fossils  in  the  quarry  rock  have 
been  found  distributed  through  several  hundred  feet  of  strata.  They 
consist  mainly  of  cephalopod  shells  which  are  closely  related  to  lower 
Beekmantown  species.  The  fauna  found  in  the  building  rock  consists 
of  a  brachiopod  and  a  trilobite  of  types  which  are  unquestionably  of  post 
Beekmantown  age.  By  fossil  evidence,  therefore,  the  age  of  the  quarry 
rock  is  established  as  older  than  the  building  rock.  This  conclusion  is 
borne  out  also  by  the  structural  relations  of  the  beds,  the  building  rock 
being  invariably  infolded  in  the  quarry  rock.  In  all  probability,  the  line 
of  contact  between  the  limestone  which  forms  the  floor  of  the  valley  and 


114      THE  CAMBRIAN  AND  ORDOVICIAN  DEPOSITS  OF  MARYLAND 

the  siliceous  formations  which  form  its  elevated  east  and  west  boundaries, 
is  in  both  cases  a  fault  plane.  There  is  little  doubt  as  to  the  faulting  on 
the  east  side,  but  the  evidence  is  not  so  convincing  on  the  west  side.  The 
succession  there  may  be  normal,  that  is,  undisturbed  with  the  Beekman- 
town  limestone  lying  unconformably  on  the  Lower  Cambrian  Harpers 
shale. 

The  Beekmantown  Limestone 

All  of  the  numerous  quarries  in  the  Frederick  Valley  operated  for  the 
burning  of  lime  expose  massive,  rather  pure,  bluish  limestones  which 
hold  fossils  of  Beekmantown  age.  The  rock  itself  is  not  unlike  that  of  the 
lower  Beekmantown  above  the  Stonehenge  member  in  the  Appalachian 
Valley,  so  that  the  use  of  the  name  Beekmantown  for  the  quarry  rock 
seems  appropriate.  It  is  even  possible  that  the  Stonehenge  member  is 
represented  here,  for  in  the  outcrops  of  Paleozoic  limestone  in  the  western 
part  of  the  valley,  namely,  along  the  trolley  car  track  two  and  one-half 
miles  northwest  of  Frederick,  strata  with  edgewise  conglomerates  are  well 
developed.  Usually,  in  this  part  of  the  valley,  these  massive  limestones 
are  covered  by  Mesozoic  red  beds.  However,  in  two  places,  erosion  has 
removed  the  red  beds  so  as  to  expose  not  only  the  quarry  rock,  but  also 
the  underlying  Harpers  shale.  One  of  these  is  in  a  small  area  two  miles 
south  of  Catoctin,  the  other  a  larger  exposure  just  east  of  Braddock. 
Fossils  were  not  observed  in  either  of  these  areas,  but  the  lithology  of  the 
limestone  is  precisely  like  that  of  the  fossiliferous  strata  a  short  distance 
to  the  east.  Moreover,  as  shown  on  the  map  (pi.  I),  an  area  of  quarry  rock 
just  east  of  Braddock  contains  an  infolded  band  of  fossiliferous  building 
rock.  Throughout  the  central  and  eastern  parts  of  the  valley  where  the 
quarry  rock  frequently  outcrops  there  can  be  no  question  regarding  the 
Beekmantown  age,  for  here  fossils  are  not  uncommon.  Along  the  eastern 
edge  of  the  valley  just  west  of  the  pre-Cambrian  schists  there  are  outcrops 
of  a  massive  light  gray  laminated  limestone  in  which  the  laminae  are 
much  contorted  and  weather  into  a  sandy  shale  somewhat  resembling  the 
shale  fragments  resulting  from  the  disintegration  of  the  upper  Stone- 
henge member  of  the  Beekmantown.  Fossils  have  not  been  discovered  in 


MARYLAND  GEOLOGICAL  SURVEY  115 

these  particular  beds,  but  these  laminated  strata  undoubtedly  represent 
a  part  of  the  Beekmantown  as  developed  in  the  Frederick  Valley. 

The  northernmost  exposures  of  the  Frederick  Valley  limestones  occur 
at  LeGore,  Maryland,  just  before  these  strata  disappear  under  the  red 
beds.  Extensive  quarrying  operations  here  have  exposed  a  considerable 
section  of  closely  folded  and  evidently  repeated  beds.  The  clue  to  the 
proper  sequence  is  given  by  several  bands  of  the  normally  overlying  thin- 
bedded  f ossilif erous  building  rock  that  are  infolded  with  the  more  massive 
Beekmantown  limestones. 

At  LeGore  the  building  rock  is  immediately  underlaid  by  about  100  feet 
of  massive  dark  blue  rather  pure  limestone  in  beds  two  to  three  feet 
thick,  alternating  with  similar  beds  of  lighter  colored  strata.  Cephalo- 
pods  of  Beekmantown  affinities  are  not  uncommon  on  the  weathered  edges 
of  these  strata.  These  upper  fossiliferous  beds  are  separated  by  about 
50  feet  of  massive  light  blue  limestone  with  quartz  grains,  from  a  lower 
fossiliferous  zone.  This  comprises  several  hundred  feet  of  strata  similar 
in  lithology  and  fossils  to  the  upper  beds.  The  section  then  continues 
for  several  hundred  feet  which  appear  to  be  a  repetition  by  folding  of  the 
strata  just  described.  Many  of  these  massive  beds  are  very  homogeneous 
and  marble-like  in  character.  The  quarries  at  Frederick  and  to  the  south 
also  afford  excellent  exposures  of  the  upper  beds  of  the  massive  lime- 
stone, but  as  the  strata  are  little  folded  here,  the  exposed  thickness  is 
consequently  slight.  On  account  of  their  ready  solubility,  outcrops  of 
these  pure  massive  limestones  appear  only  in  lowland  areas.  They  also 
leave  no  surface  residual  products  such  as  the  quartz  or  shale  fragments 
of  the  building  rock. 

The  Frederick  Limestone 

This  new  name  is  proposed  for  the  strata  in  the  Frederick  Valley  over- 
lying the  Beekmantown  limestone  and  containing  a  fauna  probably  of 
Chazyan  age.  The  rocks  are  shown  to  advantage  in  numerous  quarries 
and  natural  outcrops  around  Frederick.  Fossils  are  of  rare  occurrence 
in  these  outcrops,  but  they  may  be  found  occasionally  in  the  broad,  thin 
slabs  of  which  the  stone  fences  of  the  valley  are  built. 


116      THE  CAMBRIAN  AND  ORDOVICIAN  DEPOSITS  OF  MARYLAND 

The  Frederick  limestone  consists  of  thin-bedded  dark  blue  argillaceous 
strata  separating  into  layers  usually  less  than  two  inches  in  thickness. 
On  further  weathering,  these  leave  as  a  residual  product  in  the  soil, 
brownish-yellow  shale-like  fragments  quite  similar  to  the  weathered 
Martinsburg  shale  of  the  Appalachian  Valley.  This  limestone  is  often 
much  crumpled  and  so  seamed  with  quartz  veins  that  the  disintegration  of 
its  strata  leaves  numerous  fragments  of  white  crystalline  quartz  in  the  soil. 
In  freshly  quarried  exposures  the  Frederick  limestone  appears  massive 
and  dark  blue,  but  slight  exposure  to  the  weather  causes  its  separation 
into  the  thin  flagstones  so  much  used  in  this  area  for  building  fences  and 
embankments  that  the  local  name  of  building  rock  is  applied  to  it.  It  is 
less  soluble  than  the  associated  purer  Beekmantown  limestone,  so  that  in 
weathering  it  gives  rise  to  hill  topography  which  is  in  marked  contrast 
to  the  lowland  areas  characteristic  of  the  Beekmantown  strata.  The 
dark-blue  color,  thin  platy .  layers  of  argillaceous  composition,  upland 
topography  and  residual  quartz  fragments  distinguish  it  readily  from 
the  lighter  colored,  massive,  purer  rock  referred  to  the  Beekmantown. 

Although  numerous  exposures  of  the  Frederick  limestone  may  be  seen 
in  the  vicinity  of  Frederick,  perhaps  the  best  place  to  view  its  contact 
with  the  underlying  Beekmantown  limestone  is  at  the  Tabler  quarry 
where  a  distinct  line  of  unconformity  may  be  noted  between  the  two 
formations. 

The  thickness  of  the  Frederick  limestone  is  difficult  to  determine 
because  it  has  no  recognizable  upper  boundary  such  as  the  succeeding 
formation.  However,  in  areas  where  it  is  infolded  into  the  Beekmantown 
limestone,  its  thickness  seems  to  be  not  less  than  200  feet.  Such  infolded 
areas  are  well  shown  in  the  quarries  at  LeG-ore,  Maryland. 

Although  of  rare  occurrence  fossils  can  be  found  in  this  limestone 
more  frequently  than  in  the  subjacent  strata  because  the  opportunities 
for  collecting  are  more  numerous.  The  natural  outcrops  of  the  rock 
seldom  show  organic  remains,  but  it  is  only  a  matter  of  search  along  the 
stone  fences  of  the  Frederick  Valley  to  discover  fossils  in  the  thin  lime- 
stone layers  of  which  most  of  them  have  been  built.  Five  species  have 


MARYLAND  GEOLOGICAL  SURVEY  117 

been  noted,  only  two  of  which  are  sufficiently  preserved  for  specific 
description.  These  are  Acidaspis  ulrichi  and  Strophomena  stosei,  two 
new  species  and  an  undetermined  species  each  of  the  genera  Reteocrinus  ?, 
Cameroceras  and  Isotelus.  The  prime  interest  of  this  fauna,  like  that 
of  the  underlying  Beekmantown,  is  in  its  occurrence  east  of  the  Blue 
Ridge.  This  particular  association  of  species  is  also  noteworthy  because 
neither  the  fauna  itself  nor  the  beds  containing  it  can  be  correlated 
directly  with  any  Appalachian  Valley  formation.  However,  the  fauna 
suggests  a  Chazyan  or  early  Mohawkian  age  with  the  possibility  more  in 
favor  of  the  former. 

THE  STONES  RIVER  LIMESTONE 

The  purest  limestones  of  the  Shenandoah  series  are  contained  in  the 
strata  occurring  between  the  underlying  finely  laminated  pure  and 
magnesian  Beekmantown  formation  and  the  overlying  argillaceous 
nodular  Chambersburg  limestone  of  Black  River  age.  These  pure  lime- 
stones are  correlated  on  lithologic,  stratigraphic,  and  paleontologic 
grounds  with  the  Stones  River  group  or  formation  of  the  Central  Basin 
of  Tennessee.  In  Maryland  the  Stones  River  limestone  rests  unconform- 
ably  upon  the  Beekmantown,  the  uneven  contact  being  well  marked  by  an 
extensive  development  of  secondarily  silicified  chert  known  as  "  cauli- 
flower "  chert. 

The  Stones  River  was  named  and  defined  as  a  distinct  group  in  1855 
by  Safford,  who  based  it  on  the  limestones  outcropping  along  the  Stones 
River  in  the  vicinity  of  Murfreesboro,  Tennessee.  The  group  includes 
the  lowest  rocks  appearing  at  the  surface  in  the  Nashville  dome  of  the 
Cincinnati  axis.  Safford,  in  his  "  Geology  of  Tennessee"  (1869),  aban- 
doned the  term  under  the  misapprehension  that  the  Stones  River  rocks 
were  equivalent  to  the  Trenton  of  New  York.  Winchell  and  Ulrich,  in 
1897,  revived  the  name,  and  later  Ulrich  and  Hayes,  in  the  description 
of  the  Columbia  quadrangle  of  the  IT.  S.  Geological  Survey,  more  com- 
pletely defined  the  group. 

GENERAL  SECTIONS. — As  recognized  to-day  the  Stones  River  group  in 
its  type  area  in  Central  Tennessee  includes  the  following  formations : 


118      THE  CAMBRIAN  AND  ORDOVICIAN  DEPOSITS  OF  MARYLAND 
Formations  of  Stones  River  Group  in  the  Type  Area,  Central  Tennessee 

Fee 

Lebanon  limestone,  flaggy,  dove  and  shaly  limestone 120 

Ridley  limestone,  massive  subgranular,  often  cherty  limestone 80 

Pierce  limestone,  shaly  limestone  crowded  with  bryozoans 27 

Murfreesboro   limestone,  heavy  bedded   cherty  limestone    (base   not  ex- 
posed)   125 

In  the  gorge  of  Kentucky  Kiver  at  and  above  Highbridge,  Kentucky, 
which  cuts  through  the  oldest  rocks  to  be  seen  in  the  state,  the  lower 
200  feet  of  the  bluffs  are  made  by  massive  limestone  strata  representing 
Lebanon  and  Ridley  members  of  the  Stones  River.  In  the  Appalachian 
Valley,  rocks  corresponding  in  age,  and  also  very  closely  in  lithologic 
character  with  the  typical  Stones  River,  outcrop  in  periodically  inter- 
rupted bands  from  Alabama  to  New  York.  In  the  valley  of  East  Ten- 
nessee, where  they  attain  a  maximum  thickness  of  more  than  1200  feet, 
the  lithologic  facies  and  sequence  that  agrees  best  with  the  typical  expres- 
sion of  the  formation  is  confined  almost  entirely  to  the  western  side  of 
the  valley.  Here  a  twofold  division  may  be  recognized — a  lower  division 
of  massive,  mainly  pure,  dove  limestone  and  an  upper  division  of  more 
argillaceous  strata.  The  limestones  in  northern  Virginia,  Maryland,  and 
Pennsylvania  referred  to  the  Stones  River  agree  in  all  essential  respects 
with  these  representatives  of  the  group  in  the  south.  Here,  however,  the 
formation  is  divisible  into  three  parts,  of  which  the  lower  and  upper 
thirds  are  of  solid,  massive,  dove  limestone  and  the  middle  third  of  more 
granular  often  cherty  blue  rock  holding  the  fauna  of  which  the  large 
gastropod  Maclurites  magnus  is  the  most  characteristic  member.  The 
lower  part  is  essentially  equivalent  to  the  Murfreesboro  limestone,  the 
middle  division  to  the  Pierce  and  Ridley  beds,  and  the  upper  third  to  the 
Lebanon  limestone  of  the  type  section.  In  the  eastern  half  of  the  Appa- 
lachian Valley  in  Virginia  and  Tennessee  the  Maclurites  magnus  fauna 
occurs  and  attains  its  best  development  in  a  formation  of  argillaceous 
limestone — the  Lenoir  limestone.  In  this  part  of  the  valley  the  upper 
member  is  not  present,  so  that  here  the  Lenoir  lies  at  the  top  of  the  beds 
that  are  strictly  of  the  age  of  the  Stones  River.  Beneath  the  Lenoir  is  a 
massive  dove  limestone  formation,  the  Mosheim  limestone,  which  is  either 


•Q 


O  < 


O  < 


120      THE  CAMBRIAX  AXD  ORDOVICIAN  DEPOSITS  OF  MARYLAND 

distinctly  older  than  the  Murfreesboro  limestone  of  the  type  area  or  it 
represents  the  basal  part  of  that' formation  which  does  not  reach  the 
surface  in  central  Tennessee.  A  weak,  though  typical  representative  of 
the  Lenoir  limestone  fauna,  is  found  in  Maryland  in  the  middle  third 
of  the  Stones  River  and  it  is  probable  that  the  upper  and  lower  thirds  of 
the  formations  here  developed  represent  all  the  remaining  sedimentation 
of  Stones  River  time. 

Although  there  is  no  continuous  section  in  Maryland  where  the  com- 
plete sequence  may  be  observed,  a  generalized  section  in  areas  where  the 
three  divisions  are  well  developed  is  as  follows : 

Generalized  Section  of  Stones  River  Limestone  in  Maryland 

Feet 

Nodular,  argillaceous  strata  of  the  Chambersbur  g  limestone 

3.  Massive  and  thin  bedded  fine  grained,  pure,  dove-colored  limestone. .     300 ± 
2.  Massive  pure  limestone,  blue  to  dark  gray  in  color,  compact,  granular 
and  oolitic,  on  weathering  leaving  black,  blocky  chert;  contains 

the  Maclurites  magnus  fauna 200± 

1.  Massive  and  thin  bedded,  pure,  dove  limestone  in  the  lower  part 

interbedded  with  magnesian  layers 600± 

Light  gray,  finely  laminated  magnesian  limestone  of  Beekmantown 

age,  with  cauliflower  chert  at  top 

This  generalized  section  holds,  also,  for  southern  Pennsylvania,  but 
from  here  northward  the  Stones  River  limestone  diminishes  in  thickness 
due  to  progressive  loss  of  the  lowest  beds  by  overlap.  Between  Green- 
castle  and  Chambersburg,  Pennsylvania,  the  three  divisions  of  the  forma- 
tion have  a  combined  thickness  of  about  1000  feet.  At  Carlisle  the  lowest 
division  and  a  part  of  the  middle  are  missing,  leaving  the  formation  only 
about  450  feet  thick.  Farther  north  at  Harrisburg  the  middle  member 
has  been  diminished  by  another  hundred  feet.  Throughout  the  Lehigh 
Valley  in  Pennsylvania  and  its  continuation  in  New  Jersey,  the  Stones 
River  is  absent  altogether.  In  eastern  New  York  this  formation  is  still 
absent  until  the  upper  Champlain  region  is  reached  where  the  Stones 
River  interval  is  occupied  by  Chazyan  limestones.  The  Middle  Chazyan 
Crown  Point  limestone  contains  the  Maclurites  magnus  fauna  and  thus 
offers  a  means  of  correlation  with  the  more  southern  Stones  River 
limestone. 


MARYLAND  GEOLOGICAL  SURVEY 


CAMBRIAN  AND  ORDOVICIAN,  PLATE  XVII 


FlG.   I. — AN  AVERAGE  EXAMPLE  OF  THE  CAULIFLOWER  CHERT  FROM  THE  BASE  OF 
THE  STONES  RIVER  LIMESTONE.      VICINITY  OF  BOSTETTER,   MARYLAND. 


FlG.  2. — TYPICAL  NATURAL  OUTCROP  OF  UPPER  STONES  RIVER  LIMESTONE  IN  CLEARED 
FIELDS,  ONE-HALF  MILE  WEST  OF  PINESBURG,  MARYLAND.  THE  GROWTH  OF  CEDAR  TREES 
ON  THIS  PURE  LIMESTONE  IS  ILLUSTRATED. 


MARYLAND  GEOLOGICAL  SURVEY  121 

LITHOLOGIC  CHARACTER. — The  Stones  Eiver  rocks  in  Maryland  are  in 
general  heavily  bedded  dolomitic  layers  alternating  with  greater  thick- 
nesses of  relatively  pure  dove-colored  limestones.  In  color  and  texture 
the  purer  rock  varies  from  fine-grained  dove  to  a  dense  black  with  the 
dove-colored  rock  predominating.  Many  of  the  layers  run  as  high  in 
magnesia  as  the  underlying  Beekmantown  limestone,  but  the  Stones  River 
formation  differs  in  that  at  least  a  few  pure  dove  limestone  layers  are 
found  in  almost  every  exposure.  The  pure  limestone  is  most  abundant  at 
the  top  of  the  formation,  which  portion  therefore  is  most  extensively 
quarried.  Many  of  the  layers  throughout  the  formation  and  especially 
the  purer  strata  are  penetrated  by  the  thin  calcite  strings  belonging  to 
the  single-tubed  species  of  the  coral  Tetradium,  which,  in  connection 
with  the  smooth,  homogeneous  ground  mass  and  color  of  the  main  rock, 
gives  it  a  very  characteristic  aspect.  Another  method  of  distinguishing 
the  Stones  River  from  the  Beekmantown  lithologically  lies  in  the  char- 
acter of  the  soil  to  which  each  gives  rise  on  weathering.  The  soil  result- 
ing from  the  decomposition  of  the  Beekmantown  limestone  is  of  a  deep 
red  color,  and  generally  contains  a  considerable  quantity  of  broken  chert. 
Stones  River  rocks,  on  the  other  hand,  are  practically  free  of  chert  except 
the  middle  division ;  and  one  soon  learns  to  discriminate  this  chert  from 
all  the  varieties  formed  in  the  decomposition  of  the  Beekmantown 
limestone. 

Soil  formed  by  decay  of  Stones  River  rocks  seems  to  be  particularly 
suited  for  the  growth  of  cedar  trees.  Indeed,  the  presence  of  a  consider- 
able number  of  cedar  trees  in  an  area  of  Ordovician  strata  is  quite  a 
reliable  sign  that  the  underlying  rocks  are  of  this  age.  Of  course,  this 
preference  of  cedars  for  Stones  River  areas  is  due  primarily  to  the  nature 
of  the  rock  itself,  in  this  case,  the  pure  dove  strata  being  cedar-bearing. 
The  extensive  well-known  cedar  glades  of  central  Tennessee  are  located 
upon  the  pure,  dove-colored  Stones  River  limestone. 

PALEONTOLOGY. — Dove  limestones  which  make  up  the  greater  part  of 
the  formation  do  not  as  a  rule  afford  well-preserved  fossils,  although 
traces  of  organic  remains  in  the  rock  may  be  very  numerous.  In  fact 
some  of  these  pure  limestone  layers  are  crowded  with  gastropods,  but 


122      THE  CAMBRIAN  AND  ORDOVICIAN  DEPOSITS  OF  MARYLAND 

specimens  cannot  be  broken  out  of  the  rock  in  recognizable  condition. 
Their  cross-sections  indicate  a  general  type  of  structure  quite  unlike  and 
more  advanced  than  the  gastropods  found  in  the  underlying  Beekman- 
town  limestone.  Two  fossils,  however,  both  easily  recognized,  may  be 
found  at  almost  any  outcrop  of  this  limestone.  One  is  a  coral  formed  of 
single  tubes,  quadrangular  in  cross-section,  but  commonly  appearing  more 
like  calcite  stringers  in  the  rock  than  organic  remains.  This  is  the 
Tetradium  syringoporoides  described  on  a  later  page.  The  second  fossil 
is  a  bean-shaped  bivalved  crustacean  allied  to  Leperditia  faculties  which 
occurs  throughout  the  limestone.  Other  recognizable  fossils  occur,  but  as 
they  are  more  limited  in  their  stratigraphic  distribution,  details  regarding 
them  are  reserved  for  the  special  discussions  of  the  several  divisions. 

Lower  Stones  River. — Although  present  in  several  bands  of  outcrop 
across  Maryland,  this  portion  of  the  Stones  Eiver  is  usually  covered  and 
the  character  of  the  rocks  can  be  made  out  only  from  a  few  scattered  out- 
crops. The  best  development  is  in  the  band  of  outcrop  exposed  just  west 
of  Pinesburg  Station  and  running  north  almost  to  the  state  line.  This 
same  band  of  outcrop  is  exposed  at  Martinsburg,  West  Virginia.  Here 
many  of  the  layers,  especially  in  the  upper  two-thirds  of  the  member,  show 
sections  of  undetermined  gastropods  and  pelecypods  and  of  the  large 
ostracod  Leperditia  fabulites.  In  the  quarries  on  the  west  side  of  the 
town  which  expose  the  lower  200  feet  of  the  formation  Ulrich  reported 
certain  weathered  layers  about  125  feet  above  the  base  of  the  formation, 
from  which  he  collected  the  following  fauna : 

Fauna  of  Lower  Stones  Eiver  Limestone,  Martinsburg,  West  Virginia 

Girvanella  sp. 

Solenopora  compacta  var. 

Small,  undetermined  monticuliporoid  bryozoan 

Cyrtodonta  n.  sp. 

Matheria  n.  sp. 

Liospira  cf.  obtusa 

Lophospira  cf.  perangulata 

Lophospira  n.  sp.  of  the  L.  trochonemoides  section 

Helicotoma  f  n.  .sp. 

Orthoceras  sp.  undet.  Small,  with  narrow  septa 

Oncoceras  ?  sp.  undet. 

Leperditia  fabulites  Conrad  var. 


MARYLAND  GEOLOGICAL  SURVEY 


CAMBRIAN  AND  ORDOVICIAN,   PLATE  XVIII 


FlG.  I. — VIEW  OF  EDGEWISE  CONGLOMERATE    IN    STONES    RIVER   FORMATION   2^/2    MILES 
SOUTHEAST  OF  WILLIAM  SPORT,  MARYLAND. 


FlG.  2. — VIEW  OF  QUARRY  IN  CHAMBERSBURG  LIMESTONE  AT  PINESBURG  STATION,  MARYLAND. 


MARYLAND  GEOLOGICAL  SURVEY  123 

Traces  of  this  fauna  have  been  found  in  Maryland,  but  neither  these 
nor  the  specimens  from  West  Virginia  are  thought  well-enough  preserved 
to  warrant  illustration  and  description. 

This  lower  division  is  about  600  feet  thick  and  consists  of  massive  and 
thin-bedded  pure  dove  limestone  interbedded,  especially  toward  the  base, 
with  magnesian  layers.  Certain  parts  of  the  underlying  Beekmantown 
limestone  are  much  like  these  in  lithic  character,  but  the  presence  of 
bivalved  pelecypod  shells  in  the  Stones  River  and  their  complete  absence 
in  the  Beekmantown  serves  to  distinguish  the  two  formations.  No  well- 
exposed  section  of  the  Lower  Stones  Eiver  was  found  in  Maryland,  but  at 
Martinsburg,  West  Virginia,  the  following  section  is  more  or  less  clearly 
exposed  in  quarries  and  nearby  natural  outcrops. 

Section  of  Basal  Beds  of  Stones  River  Limestone  at  Martinsburg, 
West  Virginia 

Feet 

Strata  of  Middle  Stones  River 

Light  to  dark  drab  limestone  banded  with  thin  earthy  or  magnesian 

seams   275 

Strata  like  the  above  but  less  well  exposed 200 

Dark-gray  to  dove-colored,  fine,  even-grained  pure  limestone  (quarried) .      100 
Similar   fine-grained,   dove-colored   limestone,   increasing   downward   in 

magnesium   (quarried)    100 

Section  extends  to  the  cherty  top  of  the  Beekmantown. 

675 

Railroad  cuts  along  the  Cumberland  Valley  Railroad  north  of  Kauff- 
man,  Pennsylvania,  eight  miles  north  of  the  Maryland  line,  show  the  gen- 
eral character  of  the  division.  This  same  band  of  outcrop  continues  south- 
ward into  Maryland  and  a  number  of  localities  show  small  outcrops  of  the 
basal  rocks.  At  Bostetter  the  very  base  of  the  formation  is  exposed  at  a 
low  angle  of  dip,  with  the  result  that  a  considerable  area  here  is  covered 
with  the  cauliflower  chert  described  under  the  discussion  of  the  Beekman- 
town limestone.  This  cauliflower  chert  marks  the  base  of  the  formation 
in  the  northern  half  of  Maryland  east  of  the  Martinsburg  shale  belt, 
and  it  is  present  in  all  the  bands  of  outcrop  west  of  this  belt.  In  the 
southern  part  of  the  area  east  of  the  shale  belt,  the  Stones  River  rocks 
are  poorly  exposed  and  their  basal  beds  are  marked  by  edgewise  con- 
glomerates quite  similar  to  those  of  underlying  formations.  These  con- 


124      THE  CAMBRIAN  AND  ORDOVICIAN  DEPOSITS  OF  MARYLAND 

glomerates  occur  in  place  of  the  cauliflower  chert  which  is  so  conspicu- 
ously developed  elsewhere  in  the  valley.  Occasionally  these  basal  edgewise 
conglomerates  become  silicified,  leaving  very  interesting  chert  blocks  in 
the  soil  exhibiting  the  conglomeratic  fragments  as  pure  chalcedonic  silica, 
or  in  some  cases  showing  them  leached  out  of  the  rock  entirely. 

Middle  Stones  River. — The  middle  part  of  this  limestone  is  so  readily 
distinguished  from  the  upper  and  lower  divisions  by  its  fossils  and  lith- 
ology  that  it  might  well  be  ranked  as  a  distinct  formation.  The  Middle 
Stones  Eiver  differs  conspicuously  from  the  other  divisions  in  the  pres- 
ence of  massive  beds  of  dark,  subgranular  limestone  interbedded  with  the 
more  typical  dove-colored,  fine-grained,  pure  limestone.  Fine-grained, 
pure,  fossiliferous  limestone  weathering  so  as  to  show  numerous  bands 
of  black  chert  form  a  characteristic  part  of  this  division.  In  the  absence 
of  outcrops  an  easily  recognized  criterion  for  the  determination  of  the 
middle  division  is  the  presence  of  small  blocks  of  chert  in  the  soil.  This 
chert  is  usually  black,  at  least  the  inside  of  the  blocks  when  broken  show 
up  as  black.  Furthermore,  the  Middle  Stones  Eiver  is  generally  more 
fossiliferous  than  the  other  divisions  and  the  typical  fossil,  the  large 
coiled  gastropod  shell  Maclurites  magnus,  can  usually  be  found  in  it  after 
a  little  search. 

The  best  outcrops  for  fossils  of  the  Middle  Stones  River  are  in  the 
quarries  around  Chambersburg,  Pennsylvania,  where  the  fauna  listed 
below  was  collected  and  determined  by  Ulrich  ( Chambersburg-Mercers- 
burg  Folio).  All  of  these  species,  however,  have  been  noted  in  the 
corresponding  band  of  outcrop  in  Maryland,  although  all  have  not 
occurred  at  a  single  place.  . 

Fauna  of  the  Middle  Stones  Eiver  Limestone  in  Southern  Pennsylvania 
and  in  Maryland 

Tetradium  syringoporoides    (Ulrich) 
Hebertella  borealis  (Billings) 
Hebertella  vulgaris  (Raymond) 
Dinorthis  platys  (Billings) 
Bucania  sulcatina  (Emmons) 
Maclurites  magnus  (Lesueur) 
Lophospira  bicincta  (Hall) 
Ampyx  halli  (Billings) 
Leperditia  fabulites  (Conrad)  var. 


126      THE  CAMBRIAN  AND  ORDOVICIAN  DEPOSITS  OF  MARYLAND 

This  fauna  is  correlated  with  the  Middle  Chazy  or  Crown  Point  lime- 
stone of  New  York  and  the  Lenoir  limestone  of  southern  Virginia  and 
Tennessee,  in  each  of  which  most  of  these  species  occur. 

Upper  Stones  River. — The  upper  division  consists  of  very  pure,  thin- 
bedded,  dove-colored  or  pearl  gray  homogeneous  limestone  which  is  quite 
frequently  exposed  because  most  of  the  quarries  are  in  this  rock.  The 
large  quarry  at  Pinesburg  Station  exposes  a  considerable  thickness  of 
these  pure  upper  beds.  Here  also  sections  of  numerous  fossils  may  be 
noted,  but  the  rock  is  so  homogeneous  that  the  specimens  cannot  be 
broken  out,  and  it  weathers  in  such  a  manner  that  the  fossils  are  not  left 
in  relief  on  the  surface.  The  only  species  which  can  be  obtained  in  any 
fair  state  of  preservation  is  the  characteristic.  Stones  River  single  tube 
coral  Tetradium  syringoporoides. 

A  conspicuous  topographical  feature  of  this  portion  of  the  Stones 
River  particularly  is  the  occurrence  of  numerous  sinks  along  its  line  of 
outcrop.  However,  conditions  favoring  the  formations  of  such  sinks 
occur  also  in  the  lower  portion  of  the  Stones  River. 

AREAL  DISTRIBUTION  AND  TOPOGRAPHIC  FORM. — The  outcrops  of  the 
Stones  River  limestone  in  Maryland  are  confined  to  the  Appalachian 
Valley  and  cross  the  state  in  five  distinct  bands,  three  of  which  occur  east 
of  the  shale  belt  of  the  middle  portion  of  the  Valley,  and  two  to  the  west. 
The  strata  of  the  three  eastern  belts  are  not  as  highly  folded  as  those  to 
the  west  and  the  areas  of  outcrop  are  therefore  wider.  Each  of  these 
belts  occupies  a  nearly  level  lowland  broken  only  by  low  hills  formed  by 
the  cherty  middle  division.  In  the  northern  half  of  these  three  belts  the 
chert  and  resulting  low  hills  of  the  Middle  Stones  River  are  especially 
well  developed.  In  Maryland  this  middle  portion  has  been  noted  in  out- 
crops at  many  points.  The  residual  black  chert  is  frequently  so  abundant 
in  the  soil  that  it  leaves  its  impress  upon  the  topography  in  the  form  of 
low  hills  arranged  according  to  the  geological  structure.  This  is  illus- 
trated in  an  area  just  south  of  the  Pennsylvania  state  line  and  directly 
north  of  Hagerstown  where  the  outcrop  of  the  Middle  Stones  River 
cherty  limestone  is  plainly  indicated  by  the  low  hills  elongated  in  a 


MARYLAND  GEOLOGICAL  SURVEY 


CAMBRIAN  AND  ORDOVICIAN,  PLATE  XIX 


FlG.  I. — PHOTOGRAPH  SHOWING  SUCCESSION  OF  SINKS  ALONG  THE  BAND  OF  OUTCROP  OF  THE 
STONES  RIVER  LIMESTONE,  ONE-HALF  MILE  SOUTH  OF  WILSON,  MARYLAND.  THE  ROAD  TO  THE 
EAST  FOLLOWS  THE  CHAMBERSBURG  LIMESTONE. 


FlG.  2. — NEAR  VIEW   OF  A   SINK   FILLED  WITH   WATER. 


MARYLAND  GEOLOGICAL  SURVEY  127 

general  northeast-southwest  direction,  but  aligned  to  coincide  with  the 
general  structure  of  the  region.  In  this  same  area  the  zone  of  cauliflower 
chert  at  the  base  of  the  Stones  River  is  also  well  developed,  but  forms  no 
special  topographic  features.  With  weathering,  however,  the  chert  breaks 
up  into  smaller  and  smaller  fragments  so  that  its  presence  is  not  a. 
detriment  to  the  soil.  One  of  the  two  western  belts  lies  just  west  of  the 
Martinsburg  shale  area  and  the  second  is  a  short  belt  cut  off  by  faulting 
in  the  middle  of  the  state  and  occupies  the  center  of  the  western  half  of 
the  Great  Valley. 

Each  of  these  more  western  belts  is  quite  narrow,  because  the  rocks  are 
steeply  inclined.  Here  too  the  Middle  Stones  River  cherty  limestone  is 
not  as  clearly  developed  as  in  the  more  eastern  areas.  Rocks  outcrops 
usually  are  few,  and  the  formation  everywhere  gives  rise  to  excellent 
farm  land  soil. 

FAUNA  OF  THE  STONES  RIVER  IN  MARYLAND. — The  fossils  of  the  Stones 
River  limestone  in  its  typical  development  in  the  Central  Basin  of  Tennes- 
see have  not  received  as  much  attention  as  those  of  the  younger  Ordovician 
formations,  but  a  considerable  fauna  from  each  of  its  divisions  has  been 
collected  and  awaits  description.  The  faunas  of  the  corresponding  rocks  in 
the  Champlain  Valley  have  been  quite  fully  described  by  Raymond  in 
recent  years  and  Middle  Chazyan  faunas  have  been  recognized  farther 
south  in  the  Appalachians.  In  Maryland  the  middle  division  of  the 
Stones  River  limestone  contains  enough  Middle  Chazy  species  to  make 
it  reasonably  certain  that  these  strata  represent  the  same  time  interval. 
The  massive,  purer  dove  and  magnesian  limestone  of  the  upper  and  lower 
divisions  of  the  Stones  River  in  Pennsylvania  and  Maryland  are  not 
favorable  for  the  occurrence  of  well-preserved  fossils.  These  two  divisions 
do  not  weather  into  chert,  and  the  best  specimens  from  massive  limestone 
are  always  to  be  found  in  the  residual  cherts.  The  single-tubed  coral, 
Tetmdium  syringoporoides,  and  the  bean-shaped  ostracod,  Leperditia 
f abulites,  are  abundant  throughout  the  Stones  River  and  may  be  found 
at  almost  all  exposures.  The  other  seven  species  here  described  are  all 


128      THE  CAMBRIAN  AND  ORDOVICIAN  DEPOSITS  or  MARYLAND 


species  occurring  in  the  Middle  Chazy  of  the  Champlain  Valley.     The 
Maryland  Stones  River  fauna  and  its  occurrence  elsewhere  is  listed  below. 

FAUNA  OF  THE  STONES  RIVER  LIMESTONE  IN  MARYLAND 


Stones  River  of 
Maryland 

Lenoir 
lime- 
stone of 
Tenn. 

Middle 
Chazy  of 
Champlain 
Valley 

Lower 

Middle 

Upper 

Tetradium  syringoporoides  Ulrich  

* 

* 
* 
* 
* 
* 
* 
* 
* 
* 

* 
* 

* 
* 

• 
* 
* 

* 

* 
* 
* 
* 
* 
* 

Dinorthis  (Plaesiomys)  platys   (Billings)  .  . 
Hcbertellct'  borealis   (Billings)  . 

Hebertella  vulqaris  Raymond  

Bucanid  sulcntina  (Emmons)  

Lophospii'd  bicinctd  (Hall)  

M  dclurites  magnus  Lesueur  

4.mpyx  (Lonchodomds)  hdlli  Billings  

Leperditid  fdbulites  (Conrad)  var  

* 

The  lower  and  upper  division  of  the  Stones  River  in  Maryland,  par- 
ticularly the  latter,  frequently  exhibit  layers  crowded  with  gastropods 
and  pelecypods.  These  show  at  the  surface  as  natural  sections  and 
weather  away  as  fast  as  the  rock.  Without  a  knowledge  of  the  fauna  of 
the  similar  dove  limestone  of  the  Stones  River  elsewhere,  it  is  impossible 
to  identify  such  natural  sections  with  certainty. 

The  areas  of  the  Stones  River  limestone  east  of  the  Martinsburg  shale 
belt  have  yielded  few  fossils  because  the  rocks  weather  into  a  deep  soil 
and  outcrops  are  consequently  infrequent.  The  boundaries  of  these  areas 
have  in  most  cases  been  determined  by  the  occurrence  of  the  basal  Stones 
River  cauliflower  chert  zone.  In  northern  Maryland,  the  broad  folded 
area  of  this  formation  just  northeast  of  Maugansville  and  another  a  mile 
northwest  of  the  same  place  show  the  best  development  of  the  Middle 
Stones  River  limestone  with  the  characteristic  chert  hills  left  by  its 
weathering.  In  this  chert  all  of  the  fossils  in  the  above  list  have  been 
noted.  West  of  the  shale  belt  the  band  of  outcrop  starting  at  Pinesburg 
Station  and  going  east  of  north  through  Wilson  to  the  state  line  affords 
numerous  outcrops  of  the  dove  limestone  of  the  lower  and  upper  divisions. 
Some  of  the  layers  in  the  Upper  Stones  River  at  Pinesburg  Station  arc 


MARYLAND  GEOLOGICAL  SURVEY  129 

crowded  with  Tetradium  syringoporoides,  while  Leperditia  fabulites  and 
several  species  of  undetermined  shells  occur  in  great  number  in  other  beds* 

THE    CHAMBERSBURG   LIMESTONE 

Most  students  of  Appalachian  stratigraphy  have  recognized  a  so-called 
transition  zone  of  argillaceous  limestone  between  the  massive  limestones 
of  the  Shenadoah  group  and  the  overlying  great  shale  formation,  the 
Martinsburg  shale.  These  argillaceous  limestones  are  thin  bedded  and 
quite  fossiliferous  in  comparison  with  the  underlying  and  overlying  strata. 
They  were  classed  as  the  closing  phase  of  the  Shenandoah  group  and  their 
contained  fossils  established  the  Ordovician  age  of  the  upper  part  of  that 
group.  As  their  lithologic  character  is  clearly  enough  intermediate 
between  that  of  the  underlying  pure  and  magnesian  limestones  and  the 
typical  shale  group  above,  it  was  natural  to  believe  that  they  were  really 
transition  beds.  However,  detailed  comparison  of  the  faunas  of  these 
argillaceous  beds  in  different  parts  of  the  Appalachian  Valley  in  recent 
years  has  shown  that  these  strata  are  either  not  transition  beds  at  all  or 
that  the  supposed  transition  occurred  at  widely  different  times  in  dif- 
ferent parts  of  the  valley.  The  fossils  showed  that  as  a  rule  shale  deposi- 
tion set  in  much  earlier  in  the  eastern  bands  of  the  Appalachian  Valley 
than  in  the  western.  Also  that  these  dates  varied  considerably  even  in 
north  and  south  directions.  The  "  transition  "  beds  when  closely  studied 
proved  to  represent  formations  of  totally  different  ages  in  various  parts 
of  the  valley  and  that  stratigraphic  breaks,  sometimes  of  considerable 
extent,  commonly  separate  them  from  both  the  underlying  and  overlying 
strata.  For  example,  in  the  eastern  bands  of  the  valley  of  east  Tennessee 
this  argillaceous  limestone  phase  of  deposition  is  the  Lenoir  limestone  of 
middle  Chazyan  age,  while  at  the  western  side  of  the  valley  the  limy  beds 
just  under  the  first  shale  are  late  Trenton  in  age.  Again,  in  southern 
Pennsylvania  the  Chambersburg  limestone  of  Black  Eiver  age  directly 
or  immediately  precedes  the  Ordovician  shale  group  in  the  eastern  or 
Cumberland  Valley,  whereas  in  central  Pennsylvania  the  shale  is  under- 
lain by  uppermost  Trenton.  The  basal  part  of  the  shale  itself  varies 
correspondingly  in  age  from  upper  Chazyan  to  Utica. 


130      THE  CAMBRIAN  AND  ORDOVICIAN  DEPOSITS  OF  MARYLAND 

In  Maryland,  as  in  southern  Pennsylvania,  the  fossiliferous,  thin- 
bedded  limestone  with  argillaceous  partings,  formerly  regarded  as  the 
uppermost  division  of  the  Shenandoah  group,  is  now  called  the  Chambers- 
burg  limestone,  so  named  by  Stose  from  outcrops  in  the  vicinity  of 
Chambersburg,  Pennsylvania.  This  limestone  is  subject  to  great  varia- 
tions not  only  in  thickness,  but  in  the  character  of  the  rocks  from  place  to 
place  along  the  strike  and  across  it.  The  rather  broad  expanse  in  southern 
Pennsylvania  exposing  Cambrian  and  Ordovician  strata  exhibits  many 
outcrops  of  Chambersburg  limestone.  This  is  particularly  true  in  the 
Chambersburg  and  Mercersburg  quadrangles  in  Pennsylvania  where  good 
collections  of  fossils  have  been  made  and  numerous  sections  of  the  strata 
were  studied.  This  broad  area  of  outcrop  is  divided  by  a  wide  synclinal 
belt  of  Martinsburg  shale  that  continues  southward  through  Maryland 
into  Virginia  and  lies  in  a  continuation  of  the  Massanutten  syncline. 
As  the  towns  of  Chambersburg  and  Mercersburg  are  located  respectively 
in  the  eastern  and  western  belts,  it  has  been  found  convenient  to  term 
these  two  belts  of  outcrop  the  Chambersburg  and  Mercersburg  troughs. 
The  very  different  composition  and  thickness  of  this  formation  in  the 
two  troughs  has  been  used  by  Ulrich  in  his  Eevision  of  the  Paleozoic 
Systems  as  a  striking  illustration  of  the  instability  of  the  continental 
floor  during  Middle  Ordovician  time.  A  resume  of  these  differences  is 
presented  under  the  discussion  of  the  sections. 

LITHOLOGIC  CHARACTER. — The  Chambersburg  limestone  as  a  whole 
is  characterized  by  thin-bedded,  fossiliferous,  dark -blue,  argillaceous 
limestone  with  clayey  partings.  Many  of  its  layers  upon  weathering  have 
a  tendency  to  break  up  into  rounded  cobblestone-like  fragments.  This 
"  cobbly  "  nature  of  the  weathered  outcrop  is  so  noticeable  and  character- 
istic of  the  formation  that  it  may  be  safely  employed  in  the  discrimination 
of  this  limestone.  In  natural  or  artificial  cuts  exposing  the  weathered 
and  unweathered  zones  of  the  limestone  a  great  abundance  of  cobblestones 
at  the  surface  may  always  be  noted.  Eoads  which  happen  to  pass  along  the 
strike  of  the  cobbly  beds  where  these  are  highly  tilted  often  clearly  show 
the  arrangement  of  the  cobblestones  in  definite  thin-bedded  layers. 


MARYLAND  GEOLOGICAL  SURVEY 


CAMBRIAN  AND  ORDOVICIAN,  PLATE  XX 


FlG.    I. — TYPICAL  EXPOSURE  OF  THE   ECHINOSPHERITES  BED   OF  THE  CHAMBERSBURG  LIME- 
STONE   SHOWING   CHARACTERISTIC    COBBLY    EFFECT.       RAILROAD    CUT   AT    PINESBURG    STATION, 

MARYLAND. 


FlG.   2. — TYPICAL  OUTCROP  OF   STEEPLY   DIPPING  CHAMBERSBURG  LIMESTONE  ALONG   ROAD 
BETWEEN   PINESBURG  AND   PINESBURG   STATION,    MARYLAND. 


MARYLAND  GEOLOGICAL  SURVEY  131 

The  cobbly  effect  is  caused  by  the  clay  partings  in  the  limestone  cross- 
ing it  at  a  high  angle  so  that  weathering  breaks  up  the  solid  limestone 
into  rounded  fragments.  Also  concentration  of  the  lime  in  weathering 
and  the  relative  facility  of  its  loss  by  the  more  clayey  parts  has  much  to 
do  with  the  formation  of  the  cobbles,  as  suggested  by  Ulrich.  Fresh 
exposures,  as  in  quarries,  indicate  these  partings  very  obscurely.  The 
limestone  then  appears  massive  and  solid  and  exhibits  regular  bedding 
planes  five  or  six  inches  apart.  The  change  from  the  fresh,  massive 
limestone  to  the  cobblestones  is  well  shown  in  railroad  cuttings  where  the 
surface  outcrop  capping  the  fresh  cutting  is  preserved. 

fWsburg  Mason-.Dlxon  Gr«n<j«t-l«  Ch»™>ersbur$ 


FlG.    17. DIAGRAMMATIC   SECTION   OF  CHAMBEBSBURG  LIMESTONE   FROM   CHAMBERS- 
BURG,  PA.,  TO  STRASBTJRG,  W.  VA. 

Although  dark  blue  nodular  limestone  weathering  cobbly  constitutes 
the  greater  or  at  least  the  most  conspicuous  part  of  the  Chambersburg 
formation  in  Maryland,  other  types  of  rock  are  widely  developed  and 
often  exposed  in  the  continuation  of  the  outcrop  belts  to  the  north  and 
south.  These  strata  consist  of  interbedded  thin  calcareous  shales  and 
shaly  limestones,  thin-bedded,  dark  gray  limestone,  and  bluish  grano- 
crystalline  limestone.  All  these  strata  form  a  composite  unit  that  is 
decidedly  different  from  any  of  the  underlying  limestone  formations. 

In  Maryland  the  thickness  of  the  Chambersburg  limestone  does  not 
exceed  300  feet;  in  southern  Pennsylvania  it  reaches  a  maximum  of  800 
feet,  although  at  the  type  exposure  around  Chambersburg,  Pennsylvania, 
it  is  about  500  feet  in  thickness.  This  great  variation  is  expressed  in  the 


132      THE  CAMBRIAN  AND  ORDOVICIAN  DEPOSITS  or  MARYLAND 

diagram  on  page  131,  which  shows  that'  the  diminished  thickness  in 
Maryland  is  due  mainly  to  the  absence  of  the  lower  divisions.  . 

AREAL  DISTRIBUTION. — The  area  of  outcrop  of  the  Chambersburg  lime- 
stone in  Maryland  is  less  than  that  of  any  other  formation  west  of  the 
Blue  Eidge.  Faulting  along  the  east  side  of  the  Martinsburg  shale  belt 
has  cut  out  the  Chambersburg  limestone  everywhere  in  this  part  of  the 
valley  except  in  the  very  northern  part  of  the  state,  and  a  very  small  patch 
in  the  great  bend  of  the  Potomac  River  at  the  southern  edge. 

West  of  the  shale  belt  the  Chambersburg  outcrops  in  an  almost  con- 
tinuous band  extending  from  Pinesburg  Station  northward  to  the  Penn- 
sylvania state  line.  West  of  this  there  is  a  second  band  of  outcrop  which, 
however,  is  cut  out  by  faulting  before  half  the  state  is  traversed. 

The  outcrops  east  of  the  Martinsburg  shale  belt  give  very  little  idea 
of  the  formation,  and  in  fact  its  presence  can  be  recognized  only  by  a  few 
traces  of  cobbly,  dark-blue  limestone  showing  here  and  there  along  the 
roads  and  in  the  fields.  These  exposures  are  so  incomplete  that  it  is 
impossible  to  work  out  any  adequate  idea  of  the  sequence  and  character  of 
the  beds.  The  few  exposures,  however,  indicate  the  presence  of  the 
Echinospherites  and  Nidulites  beds  described  below. 

The  two  lines  of  outcrop  in  the  western  half  of  the  valley  afford  a  better 
opportunity  for  the  study  of  the  formation.  At  Pinesburg  Station  a  good 
exposure  of  the  rocks  may  be  seen,  particularly  the  Echinospherites  bed. 
The  road  running  north  from  Pinesburg  Station  to  Pinesburg  passes 
along  the  strike  of  these  rocks  and  numerous  outcrops  may  be  seen  on 
either  side  of  it.  At  Wilson  the  Echinospherites  bed  is  not  so  well  exposed, 
but  the  overlying  Nidulites  bed  is  well  shown  in  the  bluff  overlooking 
Conococheague  Creek.  North  of  this  is  a  rather  broad  area  of  the  forma- 
tion, but  here  the  rocks  are  hidden  to  a  great  extent  by  recent  stream 
gravels.  The  line  of  outcrop  west  .of  the  Pinesburg- Wilson  area  extends 
only  half  way  across  the  state  on  account  of  faulting,  and  exposures  are 
extremely  few  and  poor  throughout  its  length. 

FAUNAL  ZONES. — The  researches  of  Ulrich  in  the  Appalachian  Valley 
of  southern  Pennsylvania,  in  which  the  present  writer  had  an  opportunity 


MARYLAND  GEOLOGICAL  SUEVEY  133 

of  assisting,  have  shown  that  the  Chambersburg  limestone  can  be  divided 
into  six  faunal  divisions  or  members.  These  members  vary  greatly  in 
thickness  from  place  to  place,  but  retain  their  lithologic  and  faunal 
characters  with  little  change.  At  no  place  is  the  composite  section  shown 
in  the  columnar  section  developed,  but  the  strata  shown  here  represent 
all  the  sedimentation  so  far  as  known,  of  Chambersburg  age.  These  six 
divisions,  which  with  one  exception  have  received  faunal  designations  for 
convenience  of  description,  are  as  follows : 

Divisions  of  Chambersburg  Limestone  in  Pennsylvania  and  Maryland 

Feet 

6.  Greencastle  bed.    Heavy  bedded  impure  limestones 0-200 

5.  Christiania  bed.  Thin  bedded  calcareous  shales  and  shaly  limestone.  0-270 
4.  Nidulites  bed.  Compact  dark  grey  thick  and  thin  bedded  limestone.  .200-300 

3.  Echinospherites  bed.    Dark  blue  argillaceous  cobbly  limestone 40-50 

2.  Tetradium  cellulosum  bed.    Fine  grained  dove  and  subgranular  lime- 
stone        0-200 

1.  Caryocystites  bed.    Bluish  coarsely  crystalline  to  subcrystalline  lime- 
stone      0-175 

The  lithologic  and  faunal  characteristics  of  these  divisions  are  described 
in  the  following  paragraphs : 

Caryocystites  Bed. — The  lowest  division  of  the  general  time  scale  rep- 
resented in  the  typical  exposures  of  Chambersburg  limestone  consists  01 
dove-colored  and  other  limestones.  This  division  contains  the  Tetradium 
cellulosum  fauna  and  is  clearly  of  Lowville  age.  West  of  the  Martinsburg 
shale  belt  in  Pennsylvania,  the  several  bands  of  Chambersburg  limestone 
exposed  in  the  lowland  area  between  the  northern  and  southern  offsets  of 
North  Mountain  contain  a  well-defined  and  easily  recognized  lentil  of 
bluish  crystalline  limestone  reaching  a  maximum  thickness  of  175  feet. 
This  bed  wedges  in  between  the  Lowville  division  of  the  Chambersburg 
and  the  underlying  top  of  the  Stones  River.  The  abundant  occurrence  of 
a  cystid  plate  of  the  genus  Caryocystites  and  its  apparent  restriction  to 
this  division  makes  the  name  Caryocystites  bed  appropriate.  The  bands 
of  outcrop  containing  this  bed  are  not  exposed  in  Maryland,  but  are  prob- 
ably buried  under  the  younger  strata  of  North  Mountain  and  areas  to 
the  west. 


O  < 


MARYLAND  GEOLOGICAL  SURVEY  135 

Fossils  are  rare  in  the  lower  two-thirds  of  the  Caryocystites  bed,  but 
a  fauna  of  over  50  species  has  been  collected  from  the  upper  third,  particu- 
larly from  the  upper  8  or  10  feet.  As  it  is  unlikely  that  this  bed  will 
ever  be  found  exposed  in  Maryland,  it  was  thought  sufficient  for  present 
purposes  to  describe  and  illustrate  only  enough  of  its  species  to  show  its 
general  faunal  character.  It  contains  such  typical  Chazyan  brachiopods 
as  Camarotoechia  plena  (Hall)  and  Hebertella  vulgaris  Raymond,  with 
species  of  other  classes  indicating  a  similar  early  age  in  association  with 
a  few  bryozoans  and  other  fossils  that  have  been  found  elsewhere  only  in 
Black  River  deposits.  The  determination  of  the  age  of  the  bed  would 
therefore  seem  to  be  uncertain,  but  as  it  occupies  the  position  between  the 
earliest  Black  River  (Lowville)  formation  and  the  latest  Stones  River 
division  which  elsewhere  is  filled  by  Upper  Chazyan  deposits  with  similar 
faunas,  it  is  believed  advisable  to  refer  the  Caryocystites  bed  to  the 
Chazyan.  On  the  other  hand,  since  the  main  part  of  the  fauna  is  de- 
veloped only  in  the  upper  beds,  it  is  possible  that  the  entire  division  is  of 
Chazyan  age  and  that  the  upper  part  contains  an  earlier  appearance  of 
species  commonly  found  elsewhere  in  the  Black  River.  The  fauna  from 
this  bed,  as  identified  by  Ulrich,  is  listed  below.  This  faunal  list,  as  well 
as  others  of  the  Chambersburg  limestone  which  follow,  is  introduced  only 
to  give  a  general  idea  of  the  life  characteristics  of  the  various  beds.  Com- 
plete lists  of  each  division  can  only  be  published  when  a  monographic, 
study  of  the  Chambersburg  faunas  has  been  finished,  a  work  which  is  far 
beyond  the  scope  of  the  present  volume.  To  give  some  idea  of  this  fauna 
the  specifically  determined  forms  of  the  following  list  are  described  in  this 
volume. 

Fauna  of  the  Caryocystites  Bed,  Chambersburg  Limestone 

Solenopora  compacta  (Billings) 
•Columnaria  halli  Nicholson 
Tetradium  columnar ~e  (Hall) 
Carabocrinus  sp.  (plates) 
Caryocystites  sp.  (plates) 
Anolotichia  sp. 
Nicholsonella  cf.  2V.  laminata 
Batostoma  cfr.  B.  magnoporum 


136      THE  CAMBRIAN  AND  ORDOVICIAN  DEPOSITS  OF  MARYLAND 

Hemiphragma  irrasum  (Ulrich) 

Helopora  divaricata  Ulrich 

Rhinidictya  fidelis  Ulrich 

Pachydictycu  cf r.  P.  robusta 

Escharopora  confluens  Ulrich 

Graptodictya  sp.  (reticulate) 

Chasmatopora  reticulata  (Hall) 

Chasmatopora  sublaxa  (Ulrich) 

Hebertella  borealis  (Billings) 

Hebertella  vulgaris  Raymond 

Hebertella  bellarugosa  (Conrad) 

Rafinesquina  champlainensis  Raymond 

Leptaena  charlottae  Winchell  and  Schuchert 

Plectambonites  sp. 

Camarotoechia  plena  (Hall) 

Zygospira  recurvirostris  (Hall) 

Ctenodonta  cf.  C.  gibberula 

Cyrtodonta  sp. 

Gonioceras  chaziense  Ruedemann 

Leperditia  cf.  L.  faculties 

Isochilina  cf.  /.  gracilis 

Bathyurus  sp. 

Amphilichas  cf.  trentonensis 

Tetradium  cellulosum  Bed. — -One  of  the  most  widespread  Paleozoic 
formations  of  North  America  is  the  dove  limestone  of  early  Black  River 
age  known  as  the  Lowville  limestone  in  the  New  York  section.  This 
formation  has  received  various  names  in  different  parts  of  the  country, 
but  its  fauna,  and  even  its  lithology,  is  unusually  constant  throughout  an 
"area  extending  from  southern  Canada  to  Alabama  and  from  the  Appa- 
lachians to  the  Mississippi  River.  The  coral  Tetradium  cellulosum,  dis- 
tinguished by  its  colonies  composed  of  small  bunches  of  four-sided  tubes 
each  with  four  septa,  is  the  guide  fossil  of  the  formation.  In  the  Cham- 
bersburg  limestone,  the  Lowville  division  of  the  general  time  scale,  or 
the  Tetradium  cellulosum  bed,  as  it  is  here  called,  is  present  locally  and 
sometimes  reaches  a  thickness  of  as  much  as  200  feet.  As  indicated  in 
the  sections  on  other  pages,  it  usually  consists  of  fine-grained,  dove-colored 
limestone  with  some  subgranular  beds.  In  southern  Pennsylvania  the 
Lowville  forms  the  basal  member  of  the  Chambersburg  limestone  in  the 
area  between  Chambersburg  and  the  Maryland  state  line.  It  is  present- 
also  in  the  Mercersburg  belts  but  in  these  it  rests  on  the  Caryocystites 
bed.  If  represented  at  all  in  northern  Maryland,  it  is  so  thin  as  to  be 
negligible. 


MARYLAND  GEOLOGICAL  SURVEY  137 

The  fauna  of  this  zone,  as  represented  just  north  of  the  Maryland 
state  line,  contains  15  described  species,  six  of  which  are  characteristic 
Lowville  fossils  and  the  rest  Black  Eiver  forms.  The  gastropods  Helico- 
toma  planulatoides  Ulrich  and  Omospira  alexandra  (Billings)  are  par- 
ticularly characteristic  species  of  the  upper  Lowville,  but  the  coral 
Tetradium  cellulosum,  found  everywhere,  is  the  best  guide  fossil.  The 
list  of  species  discovered  by  Ulrich  in  this  bed  in  southern  Pennsylvania 
a  few  miles  north  of  the  Maryland  line  is  as  follows.  Only  traces  of  the 
Louisville  rocks  and  faunas  can  be  found  in  Maryland  and  for  that  reason 
only  the  fifteen  specifically  identified  faunas  of  this  list  are  described. 

Fauna  of  the  Tetradium  cellulosum  Bed,  Chambersburg  Limestone 

• 

Camarocladia  rugosum  Ulrich 

Beatricea  sp. 

Streptelasma  profundum  (Conrad) 

Tetradium  cellulosum  (Hall) 

Clieiocrinus  sp. 

Orbignyella  wetherbyi  (Ulrich) 

Strophomena  cf.  8.  emaciata 

Zygospira  recurvirostris  (Hall) 

Protorhyncha  sp. 

Ctenodonta  gibberula  Salter 

Cyrtodonta  sp.  .     •  . 

Helicotoma  planulatoides  Ulrich 

Helicotoma  verticalis  Ulrich 

Lophospira  cf.  L.  procera 

Omospira  alexandra  (Billings) 

Clathrospira  sp. 

Eunema  cf.  E.  salteri. 

Orthoceras  sp. 

Leper ditia  fabulites  (Conrad) 

Leperditella  tumida  (Ulrich) 

Isochilina  cf.  7.  gracilis 

Isochilina  cf.  I.  Ottawa 

Macronotella  ulrichi  Ruedemann 

Drepanella  macra  Ulrich 

Aparchites  sp. 

Primitia  so. 

Kloedenia  sp. 

Isotelus  sp. 

Pterygometopus  callicephalus  (Hall) 

Ceraurus  pleurexanthemus  Green 


139 

Echinospherites  Bed. — The  massive,  pure,  dove-colored  strata  of  the 
Stones  Eiver  limestone  are  followed  in  Maryland  by  dark  blue  argillaceous 
cobbly  limestone  which  is  never  over  50  feet  in  thickness.  In  fresh  out- 
crops, such  as  in  the  railroad  cut  at  Pin^sburg  Station,  Maryland,  this 
limestone  appears  quite  massive,  but  close  inspection  shows  thin,  shaly 
seams  dividing  the  main  mass  of  the  rock  into  dark  blue  strata.  Upon 
weathering  these  strata  give  rise  to  rounded  pieces  much  resembling  cobble 
stones.  This  feature  is  especially  characteristic  of  the  Echinospherites 
bed,  although  other  divisions  of  the  Chambersburg  limestone  exhibit 
similar  strata. 

This  bed  contains  a  few  highly  fossiliferous  bands  which  have  yielded, 
in  Pennsylvania  outcrops,  a  fauna  of  about  27  species  shown  in  the  fol- 
lowing list  published  by  Ulrich.  Of  these  the  ball  cystid  Echinospherites 
is  the  most  abundant  and  its  remains  may  be  found  at  almost  every  out- 
crop of  the  bed.  Brachiopods  and  bryozoans  of  Black  River  types  are 
associated  with  this  cystid,  although  specimens  are  much  less  abundant. 

Numerous  exposures  of  this  bed  occur  in  the  line  of  outcrop  from 
Pinesburg  Station  northward  through  Wilson  to  the  State  line,  the  best 
places  for  fossils  being  in  the  Western  Maryland  Railway  cut  at  Pines- 
burg  Station  and  the  bluffs  overlooking  Conococheague  Creek  at  Wilson. 
In  southern  Pennsylvania  excellent  exposures  of  this  bed  are  found  in  the 
railroad  cut  at  Kauffman  and  one  mile  northwest.  Excepting  the  charac- 
teristic fossil  Echinospherites,  the  fauna  of  this  bed  seems  most  closely 
allied  to  the  upper  Black  River  Decorah  shale  of  the  Mississippi  Valley 
and  for  this  reason  its  age  is  placed  as  late  Black  River.  The  species  in 
the  following  list  marked  with  an  asterisk  have  been  found  in  Maryland : 

Fauna  of  the  Echinospherites  Bed,  Chambersburg  Limestone 

Licrophycus  cf.  L.  ottawaense 

Lockeia  sp. 

*Receptaculites  occidentalis  Salter 

Ischadites  sp. 

Orocystites  ?  sp. 

tiapJianocrinus  ?  sp. 

*Echinosphcrites  aurantium  americanum  Bassler 

*Helopora  spiniformis  Ulrich 


140      THE  CAMBRIAN  AND  ORDOVICIAN  DEPOSITS  OF  MARYLAND 

*Rhinidictyd  neglecta  Ulrich 

Escharopora  cf.  ramosa 

*Prasopora  insularis  Ulrich 

*Hemiphragma  irrasum  (Ulrich) 

*Dianulites  petropolitanus  Dybowski 

Dalmanella  testudinaria  small  variety 

*Dinorthis  pectinella  (Emmons) 

*Pianodema  subaequata  (Conrad) 

*Rafinesquina  minnesotensis  Winchell 

*Rafinesquina  minnesotensis  inquassa  (Safdeson) 

Rafinesquina  sp. 

Strophomena  cf.  8.  filitexta 

Plectambonites  sp. 

Plectambonites  pisum  var. 

*Hebertella  bellarugosa  (Conrad) 

Triplecia  (Cliftonia)   simulatrix  Bassler 

Leperditia  cf.  L.  fabulites 

Pterygometopus  cf.  P.  schmidti 

*Ampyx  (Lonchodomas)  normalis  Billings 

The  Echinospherites  and  Mdulites  beds  are  well  developed  in  all  the 
sections  of  this  area,  but  the  considerable  thickening  of  the  Christiania 
bed  north  and  also  south  of  Maryland  is  a  second  interesting  feature. 
Finally,  the  occurrence  of  the  Greencastle  bed  only  in  the  area  extending 
from  the  Mason-Dixon  line  northeast  to  beyond  Chambersburg  shows 
that  local  depressions  in  an  area  can  receive  sufficient  sedimentation  rep- 
resenting a  hiatus  which  would  otherwise  hardly  be  suspected.  In  these 
various  sections  the  Upper  Stones  River  below  and  the  Sinuites  zone  at  the 
base  of  the  Martinsburg  above,  form  two  datum  planes  which  are  recog- 
nized without  difficulty. 

Nidulites-  Bed. — The  Nidulites  bed  is  the  most  conspicuous  division  of 
the  Chambersburg  in  Maryland  and  forms  the  main  part  of  the  outcrops 
of  the  formation  both  east  and  west  of  the  Martinsburg  shale  belt.  The 
heaviest  limestones  of  the  formation  are  included  in  this  bed  which,  as  a 
rule,  tends  to  weather  in  smooth,  rounded  outcrops  like  the  underlying 
massive  limestones  of  the  Stones  River  and  Beekmantown  formations, 
instead  of  the  usual  cobbly  layers.  Cobbly  layers  do  occur  in  this  bed  and 
their  weathered  outcrops  have  much  the  appearance  of  the  underlying 
Echinospherites  bed.  In  such  cases  a  brief  search  will  reveal  the  occur- 


MARYLAND  GEOLOGICAL  SURVEY  141 

rence  of  the  characteristic  fossil  of  the  Nidulites  bed,  Nidulites  pyri- 
formis,  a  pear-shaped  organism  one  to  two  inches  long,  with  the  surface 
marked  by  sharp  ridges  forming  polygonal  spaces  a  millimeter  in  diam- 
eter. This  fossil  does  not  reappear  in  the  section  until  the  Greencastle 
member  is  reached,  but  the  latter  has  not  been  identified  in  Maryland. 
These  Nidulites  are  found  throughout  the  200  to  300  feet  of  thickness  of 
the  bed,  but  they  are  most  abundant  near  the  middle  and  the  top.  The 
different  aspects  of  this  fossil  as  seen  on  weathered  surfaces  of  the  lime- 
stone are  shown  on  plate  XLVI.  Associated  with  the  Nidulites  and  in 
equal  abundance  is  a  peculiar  hemispherical  or  subglobular  bryozoan-like 
organism  described  as  Diplotrypa  ?  appalachia  in  this  volume. 

A  fauna  of  about  40  species  has  been  collected  and  identified  by  Ulrich 
from  the  excellent  exposures  of  the  Nidulites  bed  in  Pennsylvania,  but  the 
outcrops  in  Maryland  have  afforded  only  a  portion  of  these.  With  the 
exception  of  the  exposures  of  the  bed  along  the  bluffs  overlooking  Conoco- 
cheague  Creek  at  Wilson,  Maryland,  its  outcrops  in  the  state  are  usually 
weathered  edges  of  the  highly  tilted  strata  which  do  not  as  a  rule  afford 
good  fossils.  Cross-sections  of  the  Nidulites  and  Diplotrypa  can,  however, 
be  found  in  practically  every  exposure.  So  far  as  is  known  this  bed  and 
the  overlying  Christiania  and  Greencastle  beds  are  not  represented  in  the 
geological  column  elsewhere  in  North  America,  As  the  Sinuites  bed  at  the 
base  of  the  Martinsburg  shales  contain  a  fauna  of  early  Trenton  age 
and  as  the  Echinospherites  bed  underlying  the  Nidulites  bed  contains  an 
assemblage  of  species  much  like  the  upper  part  of  the  Decorah  shales  of 
the  upper  Black  River,  these  three  intervening  divisions  should  be  of  latest 
Black  Eiver  or  earliest  Trenton.  In  terms  of  the  New  York  section  these 
three  divisions  would  represent  an  age  between  the  top  of  the  Black  River 
and  the  base  of  the  Trenton.  The  species  marked  with  an  asterisk  are 
described  in  this  volume. 

Fauna  of  the  Nidulites  Bed,  Chambersburg  Limestone 

Palaeophycus  sp. 
*Nidulites  pyriformis  Bassler 
New  genus  of  Amygdalocystidae 
New  genus  of  Pleurocystidae 
Bolboporites  sp. 


142      THE  CAMBRIAN  AND  ORDOVICIAN  DEPOSITS  OF  MARYLAND 

Carabocrinus  sp.  (plates) 

Porocrinus  sp. 

*Diplotrypa  appalachia  Bassler 

Stromatotrypa  sp. 

Mesotrypa  f  sp. 

Stictoporella  ?  sp. 

*Prasopora  contigua  Ulrich 

Hemiphragma  cf.  irrasum 

*Corynotrypa  inflata  (Hall) 

*Corynotrypa  delicatula  (James) 

*OrtMs  tricenaria  Conrad 

Plectorthis  aff.  P.  whitfieldi 

Dalmanella  testudinaria  var. 

Pianodema  cf.  P.  subaequata 

*Scenidium  anthonense  Sardeson 

Strophomena  cf.  8.  ftlitexta 

Rafinesquina  cf.  R.  incrassata 

Leptaena  sp. 

Plectambonites  cf.  P.  pisum 

Plectambonites  sp. 

Triplecia  (Cliftonia)  simulatrix  Bassler 

Leperditia  cf.  L.  Jabulites 

Ampyx  cf.  A.-normalis 

Illaenus  sp. 

Pterygometopus  cf.  P.  callicephalus 

*Ceraurus  pleurexanthemus  Green 

*0nchometopus  simplex  Raymond  and  Narraway 

Christiania  Bed. — This  division  of  the  Chambersburg  limestone  is  best 
developed  on  the  east  side  of  the  Martinsburg  shale  belt  in  southern 
Pennsylvania  where  it  reaches  a  maximum  thickness  of  270  feet.  West 
of  the  shale  belt  it  is  absent  from  the  section,  but  going  southwestward 
into  Maryland  this  division  reappears  and  gradually  increases  in  thick- 
ness until  northern  Virginia  is  reached,  where  it  is  40  feet  thick.  The 
prevailing  rock  of  this  division  is  thin  bedded,  shaly  limestone  and  cal- 
careous shale  sometimes  quite  fossiliferous.  The  brachiopod  Christiania 
trentonensis  is  the  most  characteristic  of  the  described  species  and  speci- 
mens may  usually  be  found  at  its  outcrops.  In  Pennsylvania  outcrops  of 
the  Christiania  bed  have  yielded  a  fauna  of  over  40  species  which  indi- 
cates that  the  age  of  the  division  is  latest  Black  Eiver  or  earliest  Tren- 
ton. The  list  of  species,  identified  by  Ulrich,  is  given  below.  As  this  bed 
is  so  poorly  represented  in  Maryland  only  its  more  characteristic  fossils 
are  described  in  this  volume. 


MARYLAND  GEOLOGICAL  SURVEY  143 

* 

Incomplete  Faunal  List  of  the  Christiania  Bed,  Chambersburg  Limestone 

Echinospherites  aurantium  americanum  Bassler 

Crinoid  plates 

Hemiphragma  cf.  H.  irrasum 

Trematopora  cf.  primigenia 

Arthropora  bifurcata  Ulrich 

Rhinidictya  cf.  R.  neglecta 

Orbiculoidea  lamellosa  Hall 

Orthis  tricenaria  Conrad 

Scenidium  cf.  8.  anthonense 

Dinorthis  sp.  cf.  D.  subquadrata 

Strophomena  sp. 

Leptaena  cf.  L.  charlottae 

Plectambonites  sp. 

Plectambonites  pisum  Ruedemann 

Christiania  trentonensis  Ruedemann 

Triplesia  (Cliftonia)  simulatrix  Bassler 

Triplecia  cf.  T.  nucleus 

Parastrophia  hemiplicata  Hall 

Zygospira  exigua  (Hall) 

Ctenodonta  sp. 

Lepidocoleus,  2  undet.  sp.  (near  L.  jamesi) 

Illaenus  sp. 

Isotelus  gigas  Dekay 

Fragments  of  Cryptolithus  or  Tretaspis 

Greencastle  Bed. — The  thickest  sections  of  Chambersburg  limestone 
are  in  southern  Pennsylvania  in  the  vicinity  of  Greencastle,  where  200 
feet  of  heavy  bedded,  impure  limestone  follow  the  usual  Christiania  bed 
and  underlie  the  base  of  the  Martinsburg  shales.  Reference  to  the  sec- 
tions on  another  page  shows  that  this  member  can  be  recognized  as  far 
north  as  Chambersburg,  but  that  it  does  not  appear  in  any  of  the  sections 
west  of  the  Martinsburg  shale  belt.  It  appears  that  after  the  deposition 
of  the  rather  widely  distributed  Christiania  bed,  a  local  depression  in  the 
sea,  extending  from  about  the  Maryland  state  line  northward  to  and 
beyond  Chambersburg,  allowed  the  accumulation  of  this  considerable 
thickness  of  calcareous  sediments  before  the  inauguration  of  the  basal 
Martinsburg  shale.  This  division,  for  which  the  local  name  Greencastle 
bed  is  employed  for  convenience  of  reference,  is  interesting  from  a 
paleontological  standpoint,  first  because  it  contains  fossils  found  also 

10 


144      THE  CAMBRIAN  AND  ORDOVICIAN  DEPOSITS  OF  MARYLAND 

in  the  underlying  Christiania  zone  and  second  because  the  guide  fossils 
of  still  lower  members  of  the  Chambersburg  limestone,  Nidulites  and 
Echinospherites;  here  reappear  in  well  developed,  apparently  typical 
specimens.  The  number  of  species  found  in  this  bed  is  rather  large  but 
only  two  apparently  characteristic  forms,  the  cephalopods  Orthoceras 
arcuoliratum  and  Cyrtoceras  camurum,  are  described  in  the  present 
volume. 

SECTIONS  OF  THE  CHAMBEESBUKQ  LIMESTONE.— Extended  outcrops  of 
the  Chambersburg  limestone  are  so  few  in  Maryland  that  in  order  to  get 
an  idea  of  the  formation  it  is  necessary  to  study  the  exposures  in  con- 
tiguous states.  In  Maryland  there  are  only  two  places,  namely,  at  Pines- 
burg  Station  and  Wilson,  where  a  detailed  section  of  the  formation  can 
be  studied,  but  in  Pennsylvania  there  are  numerous  localities  where  all 
the  members  of  the  formation  can  be  seen  to  great  advantage. 

As  noted  above  the  formation  varies  considerably  from  east  to  west 
and  it  has  been  found  convenient  to  study  the  divisions  in  sections 
exposed  east  of  the  Martinsburg  shale  belt  and  west  of  the  same  area. 
Throughout  the  Maryland  basin  the  datum  plane  for  the  base  of  the 
Chambersburg  is  the  Upper  Stones  Eiver  dove  limestone  which  is  every- 
where developed  and  easily  recognized.  The  various  sections  quoted  below 
were  prepared  by  E.  0.  Ulrich,  with  whom  the  writer  was  associated  in 
the  study  of  this  limestone.  Most  of  them  have  since  been  published  in 
the  Chambersburg-Mercersburg  folio. 

Sections  East  of  Martinsburg  Shale  Belt  in  Pennsylvania. — Although 
the  Chambersburg  limestone  is  named  from  Chambersburg,  Pennsyl- 
vania, its  outcrops  at  this  place  are  too  few  or  incomplete  to  give  a  good 
idea  of  the  entire  section.  The  Christiania  and  Greencastle  beds  forming 
the  upper  part  of  the  Chambersburg  are  well  exposed  here,  the  Echino- 
spherites  bed  is  well  shown  along  the  railroad,  but  the  Nidulites  bed  is 
mostly  covered  and  the  Tetradium  cellulosum  bed  is  not  seen  at  all.  This 
section,  which  is  given  below,  is  particularly  interesting  in  showing  the 
development  of  the  Greencastle  bed  and  also  in  exhibiting  the  different 
faunal  zones  of  the  lower  part  of  the  Martinsburg  shale. 


MARYLAND  GEOLOGICAL  SURVEY  145 

Section  of  Martinsburg  Shale  and  Chambersburg  Limestone  Northwest  Corner 

of  Chambersburg,  Pennsylvania 
Martinsburg  shale. 

Feet 

Unfossillferous  black  fissile  shale. 

Black  shale  with  Corynoides  fauna  at  base 32 

Limy  shales  with  Cryptolithus 10 

Thin  blue  to  black  limestone  holding  the  Sinuites  fauna  at  the 

base 10 

Chambersburg  limestone. 
Greencastle  bed. 

Massive  dark  bluish  limestone 9 

Yellowish  limy  and  arenaceous  shale  with  cobbly  shaly  and 

sandy  limestones  at  base 66 

Christiania  bed. 

Shaly  limestone  with  Christiania  trentonensis  (lower  beds  of 
formation  not  exposed  in  this  section  but  shown  elsewhere 

in  vicinity) 50+ 

Nidulites  bed. 

Compact,  massive,  dark  gray  limestone 

Echinospherites  bed. 

Argillaceous  limestone  weathering  cobbly 

Tetradium  cellulosum  bed. 

Massive  fine  grained  dark  limestone 

Stones  River  limestone. 

South  from  Chambersburg  along  the  same  general  line  of  outcrop  an 
excellent  section  is  exposed  in  the  railroad  cut  two  miles  southwest  of 
Marion.  This  is  the  most  complete  and  continuous  section  of  the  forma- 
tion known  in  the  area  east  of  the  Martinsburg  shale  belt.  Fossils  are  not 
as  abundant  in  some  of  the  beds  as  they  are  elsewhere,  but  the  lithologic 
characters  of  the  different  divisions  are  well  developed  and  the  section 
exposes  all  of  the  members  recognized  east  of  the  shale  belt.  The  Green- 
castle  member,  however,  is  not  shown  in  this  particular  section  which 
ends  at  the  Martinsburg  shale  on  the  west,  but  east  of  the  section  along 
the  railroad  near  the  pike,  the  Sinuites  bed  of  lower  Martinsburg  shale  is 
underlain  by  150  feet  of  dark  gray  massive  limestone  containing  the 
fauna  of  the  Greencastle  member. 


146      THE  CAMBRIAN  AND  ORDOVICIAN  DEPOSITS  OF  MARYLAND 

Section  of  Chambersburg  Limestone  Two  Miles  Southwest  of  Marion,  Pa. 

Martinsburg  shale. 
Chambersburg  limestone. 

Greencastle  bed.  F 
Only  residual  shale  and  thin  limestone  seen.  At  the  top  are 
black  carbonaceous  limestone  and  a  thin  sandstone,  capped 
by  a  thin,  coarsely  crystalline  limestone  bed  containing 
Lingula,  representing  undoubtedly  the  Corynoides  bed 
commonly  found  near  the  base  of  the  succeeding  Martins- 
burg  shale 150 

Christiania  bed. 

Interbedded  thin  calcareous  shale  and  shaly  limestone  with  a 

few  fossils  which  indicate  the  Christiania  fauna 100 

Nidulites  bed. 

Dark,  nodular,  thin-bedded  limestone;  fossils  rare 50 

Dark,  fine-grained,  platy  limestone;    contains  Nidulites  and 

associated  fossils 94 

Compact,  dark-gray,  thick-bedded  limestone;  upper  part  very 

f ossilif erous,  containing  numerous  cystids  and  Nidulites . .     108 
Echinospherites  bed. 

Dark,  argillaceous,  cobbly  limestone,  shaly  in  lower  part;  very 
fossiliferous,  containing  a  layer  filled  with  the  ball  cystid 

Echinospherites  65 

Limestone  like  overlying  bed  but  even  darker  in  color  and 
interbedded  with  subcrystalline  limestone  layers;   fossils 

scarce   40 

Tetradium  cellulosum  bed. 

Grayish  to  dark,  dense  thin-bedded  limestone,  containing  Tet- 
radium cellulosum  and  Leperditia 150± 

Stones  River  limestone — contact  not  exposed. 

Four  miles  south  of  this  section  the  Cumberland  Valley  Bailroad  crosses 
the  Chambersburg  limestone  at  Greencastle,  Pennsylvania,  and  exposes 
the  Nidulites,  Christiania,  and  Greencastle  beds.  This  section  is  of  par- 
.ticular  interest  in  showing  the  extreme  development  of  the  Greencastle 
bed  in  the  railroad  cut  starting  at  the  bridge  just  north  of  the  town  where 
about  200  feet  mainly  of  dark  blue  massive  limestone  with  rather  numer- 
ous fossils  intervenes  between  the  typical  Christiania  bed  and  the  usual 
strata  of  the  basal  Martinsburg  shale.  The  details  of  this  section,  as 
recently  determined  by  Ulrich,  are  as  follows  • 


MARYLAND  GEOLOGICAL  SURVEY  147. 

Section  of  Upper  Divisions  of  Chambersburg  Limestone  at  Greencastle, 

Pennsylvania 

Martinsburg  shale.  Feet 

Black  fissile  shale  at  top  and  shaly  limestone  below,  not  well 

exposed ... 

Chambersburg  limestone. 
Greencastle  member. 

Rather  massive,  dark  blue  fine  grained  limestone  with  gastro- 
pods and  hemispheric  bryozoa 40      . 

Argillaceous  cobbly  limestone,  sandy  at  base 8 

Massive  grey  to  dark  blue  fine  grained  fossiliferous  limestone. 

Nidulites  abundant  at  base 50 

Massive  gray  to  blue  subcrystalline  limestone 12 

Sandy  shales    8 

Massive  granular  limestone 60 

Sandy  limestone  and  sandstone 20 

Christiania  bed. 

Argillaceous  thin  bedded  limestone  with  Christiania  trento- 

nensis,  etc.  (exposed  at  southwest  end  of  bridge) 

Nidulites  bed. 

Massive  grayish  limestone  with  Nidulites  fauna.     (Underlying 

strata  not  exposed) 

This  eastern  band  of  outcrop  continues  into  Maryland,  but  disappears 
by  faulting  about  a  mile  south  of  Cearfoss.  The  exposures  of  the'  Cham- 
bersburg in  this  part  of  Maryland  are  extremely  poor,  but  the  formation 
can  be  clearly  recognized  by  the  cobbly  appearance  of  the  weathered  rock. 
No  section  could  be  made  in  this  part  of  the  state,  nor  were  the  rocks  well 
enough  exposed  in  the  southern  part  in  the  big  bend  of  the  Potomac 
River  where  the  formation  outcrops  again. 

Sections  West  of  Martinsburg  Shale  Belt  in  Pennsylvania. — In  south- 
ernmost Pennsylvania  numerous  belts  of  Chambersburg  limestone  are 
brought  to  the  surface  by  the  geologic  structure  which  causes  the  great 
cove  in  North  Mountain  in  which  Mercersburg  is  situated.     This  low- 
land   area    affords    numerous    sections    of    the    limestone    and    many 
excellently  preserved  fossils  have  been  collected.    These  sections  are  .par- 
ticularly interesting  because  they  contain  beneath  the  Tetradium  cellulo- , 
sum  bed,  which  forms  the  base  of  the  Chambersburg  in  the  eastern  lines , 
of  outcrop,  a  subcrystalline,  massive  limestone  reaching  100  + feet  in.- 
thickness,  characterized  by  a  fauna  which  is  related  to  both  Chazyai^  arid. 
Black  River  faunas.    Another  interesting  feature  is  that  the  Christiania 


148      THE  CAMBRIAN  AND  ORDOVICIAN  DEPOSITS  OF  MARYLAND 

bed  which  is  so  well  developed  east  of  the  Martinsburg  shale  area  is  here 
entirely  wanting,  the  Mdulites.  bed  of  the  general  section  being  succeeded 
immediately  by  the  Martinsburg  shale.  The  easternmost  belt  of  outcrop 
in  this  western  area  affords  the  following  section  which  is  exposed  south 
of  St.  Thomas.  This  section  as  described  by  Ulrich  is  interesting  because 
it  is  in  the  most  easternly  belt  of  the  trough  in  which  the  Caryocystites 
bed  is  developed.  The  next  outcrop  of  the  Chambersburg  limestone  to 
the  east  contains  no  representation  of  the  110  or  more  feet  of  tho 
Caryocystites  bed  as  here  developed. 

Section  of  Chambersburg  Limestone  2y2  Miles  South  of  St.  Thomas 

Martinsburg  shale. 

Typical  dark  shale.  Feet 

Thin,  calcareous  shale,  underlain  by  calcareous  black  shale  and 

hard  thin  black  limestone  with  the  Corynoides  fauna  at  top.       31 

Coarse  granular  fossiliferous  limestone  (Sinuites  fauna) 7 

Chambersburg  limestone. 
Nidulites  bed. 

Black  cobbly  thin-bedded  fossiliferous  limestone 53 

Tetradium  cellulosum  bed. 

Massive  granular  or  finely  conglomeratic  gray,  highly  fossili- 
ferous limestone  (Beatricea  numerous) 15 

Subcrystalline,   very   fossiliferous   gray   limestone    (Leperditia 

numerous)     1 

Granocrystalline  unfossiliferous  gray  limestone,  in  part  minutely 

conglomeratic 18 

Caryocystites  bed. 

Bluish  subcrystalline  limestone  containing  numerous  Caryocys- 
tites plates  and  Solenopora  compacta 7 

Cobbly  dark  subcrystalline  limestone,  more  massive  in  upper 

part 105 

Stones  River  limestone. 

Fine  even-grained  pure  limestone,  drab  tb  dark  gray,  thin  bedded 

above,  less  pure  below 

The  railroad  cut  just  north  of  Dickey's  station,  four  or  five  miles  south- 
east from  Ft.  Loudon,  exposes  a  good  section  of  the  formation,  particu- 
larly of  the  middle  beds.  The  Echinospherites  bed  was  not  distinguished, 
but  it  is  possible  that  it  may  be  included  in  the  cobbly  limestone  at  the 
base  of  the  Nidulites  bed.  As  usual  in  these  western  bands  of  outcrop, 
the  Christiania  bed  is  missing. 


MARYLAND  GEOLOGICAL  SURVEY  149 

Section  of  Chambersburg  Limestone  One-Half  Mile  Northwest  of  Dickey,  Pa. 

Martinsburg  shale.  Feet 

Fissile  shale,  limy  at  base 

Thick  bed  of  dark-gray  coarse  crystalline  crinoidal  limestone, 

fossiliferous    (Sinuites  bed)     6 

Chambersburg  limestone. 
Nidulites  bed. 

Thin-bedded  cobbly,  dark,  fine-grained  limestone  containing 
Diplotrypa   appalachia,    Plectambonites    cf.    P.    sericeus, 

Leptaena  sp.,  Pianodema  cf .  P.  subaequata 37 

Rather  massive  gray  to  dove-colored  fine-grained  mottled  lime- 
stone banded  in  part 18 

Fine-grained  platy  to  cobbly  gray  limestone  with  few  Diplo- 
trypa         30 

Tetradium  cellulosum  bed. 

Massive  fine-grained  dark  limestone  containing  Beatricea  and 

Tetradium  cellulosum  34 

Caryocystites  bed. 

Dark    compact    subgranular    to    crystalline    limestone,    with 

Caryocystites  plates    8 

Concealed,   170  ±  feet,  of  which  probably  at  least  130   feet 

belongs  to  the  Chambersburg 130± 

Stones  River  limestone. 

Thin  bedded  pure  fine  even-grained  drab  limestone 


257± 

The  railroad  cut  just  south  of  Fort  Loudon  exposes  the  Tetradium 
cellulosum  bed  to  advantage  and  here  good  fossils  from  this  zone  can  be 
had.  Faulting  has  somewhat  confused  this  section,  but  the  locality  is 
of  particular  interest  in  showing  an  unconformable  contact  between  the 
Caryocystites  and  the  overlying  Tetradium  cellulosum  beds.  The  lowest 
six  inches  of  the  latter  consist  of  compact  clayey  limestone  rilling  irregu- 
larities in  the  surface  of  the  underlying  bed.  Evidence  of  a  time  interval 
is  also  shown  by  the  parasitic  bryozoans  and  the  expanded  bases  of 
Cleioc'nnus  which  are  attached  to  the  eroded  surface  of  the  underlying 
bed. 


150      THE  CAMBRIAN  AND  ORDOVICIAN  DEPOSITS  OF  MARYLAND 

Section  of  Chambersburg  Limestone  One-Half  Mile  South  of  Fort  London,  Pa. 

Martinsburg  shale.  Feet 

Fissile  shale  with  thin,  hard,  dark  calcareous  beds  on  fresh  ex- 
posure, 100  +  feet,  underlain  by  40  feet  of  hard  calcareous 
dark  shale  and  thin  limestones,  weathering  light  gray, 
with  graptolites  at  top. 
Sinuites  bed. 

Subgranular  black  crinoidal  limestone  containing  Sinuites  and 

Trinucleus 2 

Chambersburg  limestone. 
Nidulites  bed. 

Dark  fine-grained  limestone  weathering  cobbly 36 

Echinospherites  bed. 

Rather  dark  thin  bedded  and  shaly  limestone  with  fossils, 

among  them  fragments  of  Echinospherites . . ., 15 

Massive  dark  subgranular  limestone 12 

Tetradium  cellulosum  bed. 

Pure    dove-covered    fine    even-grained    limestone,    containing 

Tetradium  cellulosum  and  Leperditia  in  fine  conglomerate.       8 
Pure  granular  and  suboolitic  limestone,  upper  beds  coarsely 

granular;  contains  Leperditia  and  other  ostracoda 9 

Irregularly  bedded  compact  clayey  limestone  filling  irregulari- 
ties in  top  surface  of  underlying  bed.  Contains  Helicotoma 

planulatoides,  Beatricea  and  other  fossils 1 

Caryocystites  bed. 

Heavy-bedded  gray  granular  to  subcrystalline  limestone;  very 
fossiliferous;  trilobites,  brachiopods,  Caryocystites  plates, 

and  Solenopora 10 

Dark-blue  flaggy  limestone,  few  fossils 8 

Poorly  exposed  dark  granular  limestone,  estimated 100+ 

Stones  River  limestone. 

Pure  dove-colored  limestone  with  Leperditia 


200+ 

An  excellent  section  showing  the  three  divisions  usually  developed  in 
this  area  is  exposed  on  the  banks  of  the  west  branch  of  Conococheague 
Creek  two  and  one-half  miles  southeast  of  Mercersburg,  just  south  of  the 
Greencastle  turnpike.  In  this  section  the  Sinuites  zone  marking  the  base 
of  the  overlying  Martinsburg  shale  is  very  fossiliferous  and  easily  recog- 
nized. The  fine-grained,  pure  limestone  of  the  Stones  Eiver  also  clearly 
marks  the  base  of  the  formation. 


MARYLAND  GEOLOGICAL  SURVEY  151 

Section  of  Chambersburg  Limestone  on  West  Branch  of  Conococheague  Creek, 
2y2  Miles  Southeast  of  Mercersburg,  Pennsylvania 

Martinsburg  shale.  Feet 

Fissile  shale,  overlying  calcareous  black  shale  and  hard  thin 
black  carbonaceous  limestone,  containing  graptolites  and 

Lingula    

Granocrystalline,  very  fossiliferous  limestone  (Sinuites  bed) . .         2 
Chambersburg  limestone. 
Nidulites  bed. 

Cobbly  dark  subcrystalline  limestone,  both  massive  and  thin 

bedded    73 

Tetradium  cellulosum  bed  (Lowville). 

Coarse,  massive  granocrystalline  limestone  with  massive  beds 
of  pure  fine-grained  limestone  containing  Beatricea  and 

Tetradium  cellulosum  75 

Caryocystites  bed. 

Platy  granocrystalline  limestone,  very  fossiliferous 25 

Dark  subcrystalline  limestone  with  wavy  partings  of  shale; 

fossils  rare 150± 

Stones  River  limestone. 

Very  thin  bedded  pure  fine-grained  drab  limestone  underlain  by 
more  massive  pure  beds  with  magnesian  layers  and  fine 
laminations  containing  Leperditia 


323± 

In  the  few  bands  of  outcrops  of  this  limestone  in  Maryland  and  West 
Virginia  its  development  is  interesting  for  several  reasons.  First,  the 
Lowville  limestone  portion  or  Tetradium  cellulosum  bed,  and  also  the 
Caryocystites  bed  are  both  absent.  Second,  the  Nidulites  bed  forms  the 
main  mass  of  the  formation,  and,  third,  the  Christiania  bed  is  present 
west  of  the  shale  belt,  but  in  greatly  diminished  thickness. 

The  following  section  at  Pinesburg  Station,  Maryland,  is  typical  for 
the  state.  At  this  place  the  Echinospherites  bed  is  well  exposed,  but  the 
best  exposures  of  the  Nidulites  bed  are  farther  north  at  Wilson,  Maryland. 
Nowhere  are  there  good  outcrops  of  the  Christiania  bed. 

Section  of  Chambersburg  Limestone  at  Pinesburg  Station,  Maryland 

Martinsburg  shale.  Feet 

Black  fissile  shale 

Calcareous  shale  and  argillaceous  shaly  limestone  with  grapto- 
lites near  base . . 


152      THE  CAMBRIAN  AND  ORDOVICIAN  DEPOSITS  OF  'MARYLAND 

Chambersburg  limestone. 

Christiania  bed.  Feet 

Calcareous  shales  and  shaly  limestone  with  traces  of  Christiania.      10 
Nidulites  bed. 

Massive  dark  blue  to  dark  gray  limestone  with  abundant  Nidu- 
lites       270 

Echinospherites  bed. 

Thin  bedded  subgranular  limestone  weathering  cobbly  and  hold- 
ing Echinospherites  30 

Stones  River  limestone. 

Pure  dove  limestone  with  Leperditia  fabulites  and  Tetradium 

syringoporoides  

Essentially  the  same  section  is  exposed  at  Martinsburg,  West  Virginia, 
where  the  southern  continuation  of  the  same  line  of  outcrops  affords  the 
following  sequence : 

Section  of  Chambersburg  Limestone  at  Martinsburg,  West  Virginia 

Martinsburg  shale.  Feet 

Black  fissile  ehale 

Argillaceous  shaly  limestone 125 

Chambersburg  limestone. 
Christiania  bed. 

Thin  bedded  dark  gray  limestone  with  Christiania  trentonensis . .       20 
Nidulites  bed. 

Dark  gray  massive  and  thin  bedded  limestone  weathering  light 

gray  cobbly,  holding  Nidulites 300 

Echinospherites  bed. 

Dark  shaly  and  subgranular  limestone  with  Echinospherites 20 

Stones  River  limestone. 

Pure  dove  limestone 

Variations  in  Distribution. — The  distribution  of  the  various  members 
of  the  Chambersburg  limestone  in  the  eastern  and  western  parts  of  the 
Appalachian  Valley  in  southern  Pennsylvania  is  expressed  in  the  following 
table : 

General  Sequence  of  Beds  in  Chambersburg  Limestone 

West  of  Martinsburg  shale  belt  East  of  Martinsburg  shale  belt 

Greencastle  bed. 

Christiania  bed. 

Nidulites  bed    Nidulites  bed. 

Echinospherites  bed Echinospherites  be,d. 

Tetradium  cellulosum  bed Tetradium  cellulosum  bed. 

Caryocystites  bed  


MARYLAND  GEOLOGICAL  SURVEY  153 

As  noted  before,  this  area  has  been  selected  by  Ulrich  as  a  striking 
example  of  the  instability  of  the  floor  of  the  continent  during  Middle 
Ordovician  time.  The  differences  between  the  two  areas  seem  to  indicate 
that  the  eastern  half  of  the  valley  received  no  sedimentation  during 
earliest  Chambersburg  time,  while  in  the  western  half  150  feet  or  more 
of  granular  limestone  were  deposited.  During  the  periods  of  deposition 
registered  by  the  Tetradium  cellulosum,  Echinospherites,  and  Nidulites 
beds,  there  was  no  great  interruption  of  sedimentation,  but  following 
this  time  the  Christiania  bed  reaching  as  much  as  270  feet  in  thickness 
and  the  Greencastle  bed  with  a  maximum  of  200  feet  were  deposited  in 
the  eastern  half,  while  the  absence  of  such  deposits  in  the  western  half 
indicates  a  time  of  emergence.  Fig.  17,  on  page  131,  illustrates  the  un- 
equal deposition  of  these  several  beds  in  a  northeast-southwest  line  run- 
ning from  northeast  of  Chambersburg,  Pennsylvania,  to  Strasburg, 
Virginia.  The  Caryocystites  bed  is  not  present  in  any  of  these  sections 
and  the  entire  area  belongs  to  the  Chambersburg  belt  of  outcrop.  The 
thinning  of  the  Lowville  limestone  at  the  base  of  the  section  in  southern 
Pennsylvania,  its  absence  in  Maryland  and  West  Virginia,  and  its  reap- 
pearance in  northern  Virginia,  is  the  first  example  of  the  variation  in  the 
formation  along  the  strike.  The  succeeding  beds  continue  across  Mary- 
land in  varying  thicknesses  with  the  exception  of  the  Greencastle  bed, 
which  disappears  in  southern  Pennsylvania  and  apparently  does  not 
reappear  to  the  south.  Whatever  the  local  expression  of  the  Chambersburg 
limestone  may  be,  the  next  succeeding  beds  in  all  of  the  sections  are 
the  argillaceous  limestones  and  shales  of  the  overlapping  Martinsburg 
shale. 

AGE  AND  CORRELATION. — The  Chambersburg  limestone,  with  a  thick- 
ness not  exceeding  300  feet  in  Maryland,  is  the  thinnest  formation  of 
the  Cambrian-Ordovician  section  of  the  state  and  its  surface  outcrops 
are  decidedly  small  in  comparison  with  any  of  the  other  formations. 
East  of  the  shale  belt  its  areas  of  outcrop  are  so  small  as  to  be  negligible, 
and  west  of  the  same  belt  there  are  but  two  narrow  bands,  only  one  of 
which  is  continuous  across  the  state.  From  the  paleontologic  standpoint, 


154      THE  CAMBRIAN  AND  ORDOVICIAN  DEPOSITS  OF  MARYLAND 

however,  the  Chambersburg  limestone  is  most  important  since  its  con- 
tained faunas  are  more  numerous  in  species  and  individuals  than  any 
other  formation. 

Just  north  of  the  Maryland-Pennsylvania  state  line  the  areas  of  out- 
crop of  the  Chambersburg  limestone  are  not  only  more  numerous,  but 
also  often  broader.  Here  also  natural  and  artificial  cuttings  have  af- 
forded much  better  opportunities  to  study  the  formation  and  to  collect 
its  faunas.  The  identification  of  the  Chambersburg  fossils  described  in 
the  following  pages  has  been  based  primarily  upon  the  much  better  pre- 
served material  from  Pennsylvania,  although  the  Echinospherites  and 
Mdulites  beds  in  Maryland  have  yielded  equally  good  faunas.  The 
divisions  of  the  Chambersburg  limestone  and  their  approximate  position 
in  the  time  scale  are  as  follows : 

Divisions  of  Chambersburg  Limestone  in  Pennsylvania  and  Maryland 

Greencastle  bed   (Late  Black  River  or  Early  Trenton) 

Christiania  bed  (Late  Black  River) 

Nidulites  bed  (Late  Black  River) 

Echinospherites  bed  (Late  Black  River) 

Tetradium  cellulosum  bed  (Early  Black  River-Lowville) 

Caryocystites  bed  (Upper  Chazyan  or  Earliest  Black  River) 

The  relations  of  these  faunas  to  each  other  and  the  distribution  of  their 
strata  in  different  portions  of  the  middle  Appalachian  valley  have  been 
described  on  previous  pages. 

UPPER  ORDOVICIAN  SHALES 
THE  MARTINSBURG  SHALE 

The  shale  phase  of  sedimentation  which  concludes  Ordovician  deposi- 
tion in  the  Middle  Appalachians  is  best  known  from  outcrops  in  the 
middle  of  the  Great  Valley  where  these  strata  occupy  part  of  the  well- 
known  syncline  named  from  Massanutten  Mountain  in  Virginia.  Mar- 
tinsburg,  West  Virginia,  lies  on  the  western  edge  of  this  syncline,  whence 
the  name  for  this  shale  formation.  The  Massanutten  syncline  crosses 
Maryland  in  a  southwest-northeast  direction,  occupying  an  area  several 


156      THE  CAMBRIAN  AND  ORDOVICIAN  DEPOSITS  or  MARYLAND 

miles  wide  just  west  of  Williamsport.  In  its  course  through  Maryland, 
Conococheague  Creek  is  confined  to  this  belt  of  Martinsburg  shale,  and 
the  rugged  topography  caused  by  its  erosion  affords  many  outcrops  of  the 
'strata.  Exceptionally  fine  exposures  occur,  however,  along  the  Western 
Maryland  Railway  from  Williamsport  west  to  Pinesburg  Station.  The 
underlying  shale  rock  is  shown  almost  continuously  between  these  two 
places.  Perhaps  nowhere  else  in  the  Appalachian  Valley  is  there  such  a 
continuous  section  of  this  formation  exposed  with  all  its  attendant  fold- 
ing and  faulting,  and  these  railroad  cuts  will  long  remain  classic  ground 
for  the  study  of  this  great  syncline. 

This  section  clearly  brings  out  two  well-marked  divisions  in  the  forma- 
tion, the  lower  part  consisting  of  a  thick  mass  of  black  shale,  and  the 
upper  portion  for  the  most  part  of  yellowish-green  sandy  strata.  These 
two  portions  are  distinct  enough  in  the  Massanutten  syncline  to  be 
mapped  as  separate  divisions,  but  in  the  North  Mountain  uplift  to  the 
west  they  grade  into  each  other  so  gradually  that  it  is  impossible  to  map 
them  separately. 

Sufficient  fossil  evidence  has  been  found  in  Maryland,  but  especially  in 
southern  Pennsylvania,  to  show  that  these  two  lithologic  divisions  corre^ 
spond  to  definite  portions  of  the  general  time  scale.  The  lower  black 
shale  division  contains,  near  the  base,  several  horizons  with  faunas  of 
Trenton  age.  It  is  probable,  although  not  yet  established  by  paleon- 
tologic  evidence,  that  the  upper  part  of  these  black  shales  corresponds  to 
the  Utica  shale  of  the  New  York  section.  In  the  area  west  of  the  Massa- 
nutten syncline  the  sandy  division  has  furnished  numerous  fairly  well 
preserved  fossils  of  Eden  age.  In  the  North  Mountain  uplift  this  sandy 
Eden  division  is  followed  by  gray  sandstones  with  a  maximum  thickness 
of  450  feet  in  which  a  considerable  number  of  Cincinnati  an  (Lower  May?- 
ville)  fossils  has  been  found.  These  gray  sandstones  are  still  included  in 
the  Martinsburg  shale,  but  the  overlying  soft  red  sandstone  and  red  shale 
are  so  distinct  that  they  have  been  separated  as  the  Juniata  formation. 
The  Martinsburg  shale  as  here  developed,  therefore,  ranges  in  age  from 
the  Lower  Trenton  to  at  least  the  Lower  Maysville  and  comprises  portions 
of  the  Mohawkian  and  Cincinnatian  series. 


157 

LITHOLOGIC  CHAEACTEKS  AND  SECTIONS. — As  just  noted  above,  the 
Martinsburg  shale  consists  in  general  of  black  shale  forming  the  lower 
division  and  light-colored  sandy  shales  the  upper,  but  its  lowest  beds  are 
of  thin-bedded  limestone  and  calcareous  shale,  while  the  uppermost  beds 
are  gray  sandstone.  The  formation  thus  includes  a  variety  of  rock  types, 
but  shale  is  the  predominating  rock,  so  that  the  lithologic  designation 
"  shale  "  for  the  formation  as  a  whole  is  appropriate.  Depending  more 
particularly  on  fossil  evidence,  four  distinct  divisions  can  be  recognized 
in  this  shale,  although  all  may  not  be  present  in  the  same  section.  These 
divisions  with  their  approximate  thicknesses  are  expressed  in  the  fol- 
lowing general  section : 

General  Section  of  the  Martinsburg  Shale  in  Southern  Pennsylvania 
and  Maryland 

Juniata  Formation  of  Earliest  Silurian  or  Highest  Ordovician  Age. 

Martinsburg  shale. 

Upper  Maysville  division.  Feet 
Unfossiliferous    sandstone    (Oswego   sandstone).      (Probably 
represented  under  cover  west  of  North  Mountain,  in  Mary- 
land)      150 

Lower  Maysville  division. 

Fossiliferous  gray  sandstone  with  Orthorhynchula  linneyi  bed 
at  top.     (Probably  present  west  of  North  Mountain  under 

cover)     300 

Eden  division. 

Yellow  shale  and  calcareous  sandstone  interbedded,  with  upper 

Eden  fossils 500± 

Soft  greenish  to  yellow  shaly  sandstones  and  shale  with  Eden 

fossils  not  uncommon  at  several  horizons 500 ± 

Trenton  and  ?  Utica  division. 

Dark-gray  unfossiliferous  shale  breaking  up  into  "  shoe  peg  " 

fragments  and  often  weathering  into  soft  whitish  clay. . .     500 ± 

Black  carbonaceous  fissile  unfossiliferous  shale 500± 

Calcareous  dark  shale  and  thin  limestone  weathering  gray 

containing  graptolites  (Corynoides  fauna) .20-100 

Granocrystalline  fossiliferous  limestone  and  shale  holding  the 

Sinuites  fauna 2-10 

Chambersburg  limestone    


Total    2500± 


158      THE  CAMBRIAN  AND  ORDOVICIAN  DEPOSITS  OF  MARYLAND 

Although  the  above  section  applies  in  general  to  all  of  the  Martinsburg 
shale  areas  in  Maryland  and  adjoining  states,  a  conspicuous  exception  to 
the  development  of  tha  Eden  division  is  to  be  noted  in  the  Massanutten 
syncline  area.  Here  the  lower  part  is  the  usual  thick  mass  of  black 
carbonaceous  shale  with  the  Sinuites  bed  at  the  base  and  the  Corynoides 
bed  higher,  but  the  upper  portion  consists  of  yellowish-green  speckled 
sandstone  so  easily  recognized  that  it  has  been  mapped  as  a  separate 
member.  On  fresh  exposure  this  rock  is  found  to  be  a  greenish-gray 
arkose  of  feldspar  and  sand  with  the  speckled  appearance  due  to  the 
weathering  of  the  feldspar  into  kaolin.  Small  streams  draining  into 
Conococheague  Creek  have  cut  very  rugged  picturesque  ravines  in  these 
strata. 

The  black  carbonaceous  shale  becomes  quite  calcareous  at  the  base  and 
appears  to  grade  into  the  underlying  Chambersburg  limestone.  How- 
ever, a  distinct  line  of  unconformity  separates  the  two  formations  as 
evidenced  ^by  the  varying  age  of  the  topmost  bed  of  the  Chambersburg 
in  different  parts  of  the  valley.  Fossils  are  sometimes  abundant  in  these 
basal  calcareous  beds  of  the  shale  and  the  frequent  occurrence  of  the 
gastropod  Sinuites  gives  its  name  to  the  bed.  A  fauna  of  almost  50 
species  has  been  recognized  in  the  Sinuites  bed  of  Pennsylvania  and 
Virginia,  but  in  Maryland  the  bed,  although  recognized,  has  yielded 
few  fossils. 

Thirty  or  more  feet  above  the  base  of  the  shale  a  second  f aunal  zone  is 
encountered.  Here  the  small  comma-shaped  graptolite  Corynoides  is  so 
abundant  that  it  forms  a  convenient  designation  for  the  bed.  This  Cory- 
noides bed  has  been  recognized  in  several  places  in  Maryland  particularly 
at  Williamsport  and  at  Pinesburg  Station 'on  the  east  and  west  sides 
respectively  of  the  Massanutten  syncline.  This  fauna  is  small  in  num- 
bers, but  it  constitutes  an  interesting  horizon  throughout  this  part  of  the 
Appalachians. 

Following  the  Corynoides  bed  are  the  typical  black  carbonaceous  and 
dark  gray  unfossiliferous  shales  of  the  lower  Martinsburg  which  are  so 
readily  recognized  on  surface  outcrops  by  the  "  shoe  peg  "  fragments  left 


11 


160      THE  CAMBRIAN  AND  ORDOVICIAN  DEPOSITS  OF  MARYLAND 

by  weathering.  In  fresh  exposures  these  beds  are  hard  and  sometimes 
reach  several  feet  in  thickness,  but  weathering  brings  out  the  intense 
squeezing  and  folding  to  which  they  have  been  subjected.  Slaty  cleavage 
usually  obscures  the  original  bedding,  but  occasionally  a  weathered  sur- 
face clearly  shows  the  relation  between  cleavage  and  stratification.  The 
rock  breaks  down  into  small  fragments  not  unlike  shoe  pegs  and  finally 
weathers  into  soft  whitish  clay.  With  the  introduction  of  sandy  sedi- 
ments in  the  Martinsburg  shale,  fossils  again  are  encountered  and  give  a 
clew  as  to  the  age  relations.  At  least  three  distinct  fossiliferous  zones 
.have  been  discovered  in  these  upper  sandy  shales.  Two  of  these  contain 
numerous  species  characterizing  the  Eden  division  of  the  Cincinnatian, 
whereas  the  third  zone  shows  fossils  of  Lower  Maysville  age.  As  noted 
before,  these  fossiliferous  zones  are  encountered  only  in  areas  west  of  the 
Massanutten  syncline  as  the  conditions  for  the  preservation  of  organic 
remains  were  not  favorable  during  the  deposition  of  the  sandy  strata  in  the 
syncline  itself. 

Because  of  the  lack  of  good  exposures  of  the  upper  Martinsburg  in  the 
mountainous  areas  of  western  Maryland,  it  has  not  been  possible  to  pre- 
pare detailed  sections  showing  the  position  of  the  fossiliferous  beds 
accurately.  In  southern  Pennsylvania,  however,  especially  in  the  vicinity 
of  McConnellsburg  and  Fort  Loudon,  there  are  several  extensive  exposures 
of  these  beds.  In  the  Eden  portion  of  the  Martinsburg  shale  42  species 
have  been  recognized. 

The  interval  between  the  top  of  the  formation  and  the  highest  zone 
in  which  Eden  fossils  were  found  is  occupied  by  gray  sandstone  about 
450  feet  thick.  This  is  locally  divisible  into  two  unequal  parts,  the  lower 
300  feet  thick,  the  upper  150  feet,  by  a  fossiliferous  stratum  in  which  the 
brachiopod  Ortliorhyncliula  linneyi  is  a  common  fossil.  Elsewhere  in  the 
Appalachian  Valley  and  in  the  Ohio  Valley  this  Orthorhynchula  bed  lies 
near  the  top  of  the  Lower  Maysville.  This  fossil  zone  has  yielded  a  fauna 
of  18  species  in  southern  Pennsylvania,  all  of  which  are  characteristic 
Lower  Maysville  fossils.  The  overlying  unfossiliferous  gray  sandstone 


MARYLAND  GEOLOGICAL  SURVEY 


CAMBRIAN  AND  ORDOVICIAN,  PLATE  XXI 


FlG.  I. — VIEW  IN  THE  TABLER  QUARRY  JUST  SOUTH  OF  FREDERICK,  MARYLAND, 
SHOWING  THE  MASSIVE  BEEKMANTOWN  LIMESTONE  OVERLAID  BY  THE)  THIN-BEDDED 
FREDERICK  LIMESTONE  WITH  A  DISTINCT  LINE  OF  UNCONFORMITY  SEPARATING  THEM. 


FlG.  2. — FOLD  IN  SANDY  UPPER   (EDEN)   PORTION  OF  MARTINSBURG  SHALE  ALONG  WESTERN 
MARYLAND  RAILWAY,  THREE-FOURTHS    MILE  WEST  OF   WILLIAMSPORT,   MARYLAND^ 


MARYLAND  GEOLOGICAL  SURVEY  161 

bringing  Martinsburg  shale  deposition  to  a  close  is  equivalent  on  strati- 
graphic  grounds  to  the  Oswego  sandstone  of  New  York,  and  like  it,  is 
apparently  either  of  continental  origin  or  its  formation  is  connected  with 
some  phase  of  sea  withdrawal.  It  is  fairly  well  agreed  upon  by  geologists 
that  the  Juniata  shales  or  Eed  Medina  immediately  following  the  Oswego 
sandstone,  is  a  continental  expression  of  the  marine  Richmond  group  of 
the  Ohio  Valley.  Indeed  the  two  formations  have  actually  been  traced 
into  each  other.  The  underlying  fossiliferous  Upper  Maysville  (Mc- 
Millan) formation  of  the  Ohio  Valley,  which  occurs  between  the  Richmond 
above  and  the  Orthorhynchula  bed  at  or  near  the  top  of  the  Lower  Maysville 
(Fairview)  below,  is  thus  almost  certainly  the  equivalent  of  the  un- 
fossiliferous  Oswego  sandstone  which  has  the  same  boundary  planes. 
This  correlation  is  further  indicated  by  the  fact  that  in  both  instances  the 
Lower  Maysville  strata  pass  into  the  Upper  Maysville  without  any  clear 
evidence  of  a  stratigraphic  break. 

TOPOGRAPHIC  FEATURES  AND  AREAL  DISTRIBUTION. — The  largest  area 
of  Martinsburg  shale  in  Maryland  forms  a  low  plateau  averaging  two 
and  one-half  miles  in  width.  This  crosses  the  state  in  a  belt  trending 
southwest-northeast  through  the  central  part  of  the  Appalachian  Valley. 
These  shales  resist  weathering  much  more  effectively  than  the  subjacent 
limestones,  the  result  being  the  low,  yet  topographically  conspicuous 
plateau  already  mentioned.  Although  it  is  much  dissected  by  Conoco- 
cheague  Creek  and  its  tributaries,  the  upland  part  of  this  plateau  has  an 
altitude  of  about  580  feet  at  the  Mason-Dixon  line,  but  descends  to  about 
540  feet  at  the  Potomac  River.  These  upland  areas  are  remnants  of  an 
old  peneplain  that  is  still  well  preserved  in  the  vicinity  of  Harrisburg, 
Pennsylvania,  and  after  which  it  has  been  named.  The  excellent  and 
almost  continuous  exposures  of  the  Massanutten  syncline  belt  of  Martins- 
burg shale  along  the  Western  Maryland  Railway  between  Williamsport 
and  Pinesburg  Station  have  been  mentioned  before. 

In  the  limestone  valley  west  of  the  Massanutten  syncline  a  narrow  strip 
of  this  shale  has  been  brought  down  to  the  surface  by  faulting.  The  only 


MARYLAND  GEOLOGICAL  SURVEY  163 

• 

other  areas  in  Maryland  are  in  the  North  Mountain  uplift,  one  forming 
the  eastern  slope  of  Powell  Mountain,  a  second  occupying  Blair  Valley 
between  Rickard  and  Sword  Mountains,  and  the  third  and  smallest  being 
the  Punchbowl  area  of  Bear  Pond  Mountain.  These  North  Mountain  areas 
show  few  outcrops  of  rock  and  are  generally  covered  by  debris  of  the 
sandstone  formations  which  form  the  tops  of  the  adja'cent  mountains. 

FAUNAS. — Although  fossils  must  be  considered  as  quite  rare  in  the 
Martinsburg  shale,  sufficient  paleontologic  evidence  has  been  found  to 
show  that  faunas  of  Trenton,  Eden,  and  Maysville  age  are  represented. 
Two  zones  with  Trenton  fossils  occur  near  the  base  of  the  formation,  the 
Eden  fauna  is  found  in  the  upper  sandy  portion,  and  the  topmost  sand- 
stones hold  Maysville  species. 

Fauna  of  the  Basal  Martinsburg  Shale  (Sinuites  Bed  of  Trenton  Age.) 
The  most  prolific  zone  for  fossils  in  the  Martinsburg  shale  is  a  thin 
band  of  limestone  near  the  base  of  the  formation  which  locally  is  crowded 
with  organic  remains.  This  zone  has  been  recognized  at  numerous  places 
in  southern  Pennsylvania,  Maryland,  and  Virginia,  although  exposures  of 
it  are  less  frequent  in  Maryland  and  its  contained  fossils  here  are  quite 
few  in  comparison  with  the  other  two  states.  In  southern  Pennsylvania 
the  35  species  described  in  the  following  pages  have  been  found  repre- 
sented by  fairly  good  specimens,  while  an  additional  dozen  or  more  forms 
are  known  from  poorly  preserved  fragments.  A  still  larger  fauna  occurs 
in  this  bed  at  Strasburg,  Virginia,  where  excellent  exposures  for  collect- 
ing occurred  in  the  past. 

The  most  striking  and  common  fossil  of  this  zone  is  the  gastropod 
Sinuites  cancellatus  which  has  given  rise  to  the  name  of  the  Sinuites  bed. 
In  the  Chambersburg-Mercersburg  folio  of  the  U.  S.  Geological  Survey, 
this  zone  has  been  considered  as  a  transition  bed  between  the  Black  River 
and  Trenton  and  placed  at  the  top  of  the  Chambersburg  limestone.  As 
indicated  later  by  Ulrich  in  his  Revision  of  the  Paleozoic  Systems,  the 
early  Trenton  aspect  of  its  fauna  is  more  marked  than  that  of  the  Black 
River,  and  the  reference  of  the  bed  to  the  basal  Martinsburg  is  believed  to 


164      THE  CAMBRIAN  AXD  ORDOVICIAN  DEPOSITS  or  MARYLAND 

be  more  correct.  Stratigraphic  evidence  also  shows  that  the  Siimites 
bed  follows  a  considerable  interruption  of  deposition,  since  the  thickness 
of  strata  between  it  and  the  Nidulites  bed  of  the  Chambersburg  is  most 
variable. 

The  best  localities  for  obtaining  collections  of  the  Sinuites  fauna  are 
just  north  of  the  Mason-Dixon  line  in  southern  Pennsylvania.  East  of 
the  Martinsburg  shale  belt  in  this  region  the  following  fossils  have  been 
found : 

Fauna  of  Basal  Martinsburg  Shale  (Sinuites  Bed),  Chambersburg 

Quadrangle 

Lingula  riciniformis  Hall 
Leptobolus  ovalis  n.  sp. 
Conotreta  rusti  Walcott 
Strophomena  sculpturata  n.  sp. 
Dalmanella  testudinaria  (Dalman)  var. 
Microceras  inornatum  Hall 
Sinuites  cancellatus  Hall 
Sinuites  granistriatus  Ulrich 
Cyclora  minuta  Hall 
Cyclora  parvula  (Hall) 
Cyclora  hoffmani  Miller 
Coleolus  iowensis  James 
Conularia  trentonensis  Hall 
Orthoceras  junceum  Hall 
Trocholites  ammonius  Conrad 
Eoharpes  ottawaensis  (Billings) 
Cryptolithus  tesselatus  Green 
Triarthrus  flscheri  Billings 
Triarthrus  ftecfci  Green 
Bumastus  trentonensis  Emmons 
Proetus  latimarginatus  Weller 
Cyphaspis  matutina  Ruedemann 
Calymene  senaria  Conrad 

West  of  the  shale  belt  in  the  Mercersburg  quadrangle  a  larger  number 
of  species  has  been  identified  in  the  Sinuites  zone,  but  many  of  them  are 
identical  with  those  in  the  more  eastern  belt  of  outcrop. 


MARYLAND  GEOLOGICAL  SURVEY 


CAMBRIAN  AND  ORDOVICIAN,  PLATE  XXII 


FlG.  I. — EXPOSURE  OF  LOWER  PART  OF  MARTINSBURG  SHALE  ALONG  WESTERN  MARYLAND 
RAILWAY,  ABOUT  ONE-HALF  MILE  EAST  OF  PINESBURG  STATION,  MARYLAND.  THE  GENTLE 
DIP  OF  THE  STRATA  AND  THE  CLEAVAGE  AT  RIGHT  ANGLES  ARE  WELL  SHOWN. 


.  2. — VIEW  ACROSS  VALLEY  OF  CONOCOCHEAGUE  AND  BEEKMANTOWN  LIMESTONES,  FROM 
A  POINT  TWO  MILES  EAST  OF  LITTLE  GEORGETOWN,  WEST  VIRGINIA.  CONOCOCHEAGUE  CHERT 
STREWS  THE  FOREGROUND.  NORTH  MOUNTAIN  IN  THE  DISTANCE  CONTAINS  THE  JUNIATA 
AND  TUSCARORA  FORMATIONS. 


MARYLAND  GEOLOGICAL  SURVEY  165 

Fauna  of  Sinuites  Bed  in  Mercersburg  Quadrangle,  Pennsylvania 

Hindia  parva  Ulrich 
Lingula  riciniformis  Hall 
Leptobolus  ovalis  n.  sp. 
Dalmanella  testudinaria  (Dalman)  var. 
Dalmanella  edsoni  n.  sp. 
Christiania  lamellosa  n.  sp. 
Strophomena  sculpturata  n.  sp. 
Leptaena  tenuistriata  Spwerby  var. 
Tripleciv,  (Cliftonia)  simulatrix  n.  sp. 
Scenidium  ?  merope  (Billings) 
Cyrtolitina  nitidula  (Ulrich) 
Microceras  inornatum  (Hall) 
Sinuites  cancellatus  (Hall) 
Sinuites  granistriatus  (Ulrich) 
Strophostylus  textilis  Ulrich  and  Scofield 
Cyclora  hoffmanni  Miller 
Cyclom  minuta  Hall 
Cyclora  parvula  (Hall) 
Eccyliomphalus  trentonensis  (Conrad) 
Coleolus  iowensis  James 
Orthoceras  junceum  Hall 
Spyroceras  bilineatum  (Hall) 
Cryptolithus  tesselatus  Green 
Triarthrus  becki  Green 
Illaenus  americanus  Billings 
Cyphaspis  matutina  Ruedemann 
Amphilichas  trentonensis  (Conrad) 

The  complete  list  of  identified  species  in  the  Sinnites  bed  with  their 
occurrence  in  the  best  localities  for  collecting  in  southern  Pennsylvania  is 
shown  in  the  table  on  next  page. 

Fauna,  of  the  Lower  Martinsburg  Shale  (Corynoides  Bed  of  Trenton 
Age). — Thirty  feet  or  more  of  unfossiliferous  black  calcareous  shale  and 
thin-bedded  limestone  overlie  the  Sinuites  bed  and  are  in  turn  followed  by 
a  fossiliferous  zone  crowded  with  graptolites  and  other  organisms,  some  of 
which  have  a  Utica  aspect,  although  the  majority  are  known  in  the  Tren- 
ton limestone.  The  abundant  occurrence  of  the  small,  peculiar  graptolite 
Corynoides  calicularis  in  this  zone  occasions  its  name.  A  second  char- 


166      THE  CAMBRIAN  AND  ORDOVICIAN  DEPOSITS  OF  MARYLAND 


FAUNA  OF  THE  SINUITES  BED 


Chambers- 
burg,  Pa. 


5  m.  SSW. 
Chamberb- 
burg,  Pa. 


2  m.  S.  St. 
Thomas, Pa. 


3  m.  SE. 
Mercers- 
burg,  Pa. 


Hindia  parva  Ulrich 

Lingula  riciniformis  Hall i        * 

Leptobolus  ovalis  n.  sp j        * 

Gonotreta  rusti  Walcott 

Dalmanella  tcstudinaria  (Dalman)  var * 

Dalmanella  edsoni  n.  sp ;#. 

Christiania  lamellosa  n.  sp 

Strophomena  sculpturata  n.  sp # 

Leptaena  tenuistriata  Sowerby  var j 

Triplecia  (Cliftonia)  simulatrix  n.  sp 

Scenidium  ?  merope  (Billings) 

Cyrtolitina  nitidula  (Ulrich) \, 

Microceras  inornatum  (Hall) 

Sinuites  cancellatus  (Hall) 

Sinuites  granistriatus  (Ulrich) i        # 

Strophostylus  textilis  Ulrich  and  Scofield.  . 

Cyclora  minuta  Hall 

Cyclora  parvula  (Hall) 

Cyclora  hoffmanni  Miller 

Eccyliomphalus  trentonensis  (Conrad) 

Coleolus  iowensis  James 

Conularia  trentonensis  Hall 

Orthoceras  junceum  Hall * 

Spyroceras  bilineatum  (Hall) 

Trocholites  ammonius  Conrad * 

Eoharpes  ottawaensis  (Billings) 

Cryptolithus  tesselatus  Green * 

Triarthrus  fischeri  Billings 

Triarthrus  becki  Green . 

Illaenus  americanus  Billings 

Bumastus  trentonensis  Emmons * 

Proetus  latimarginatus  Weller * 

Cyphaspis  matutina  Ruedemann 

Amphilichas  trentonensis  (Conrad) 

Calymenc  senarii  Conrad 


MARYLAND  GEOLOGICAL  SURVEY  167 

acteristic  fossil  is  the  pod-shaped  crustacean  Caryocaris  silicula,  indi- 
viduals of  which  are  often  quite  common  in  the  shaly  limestones. 

The  Corynoides  bed  has  been  recognized  in  the  Appalachian  Valley 
from  Pennsylvania  south  to  Virginia.  In  Maryland  the  shale  outcrops 
in  the  vicinity  of  Williamsport  and  Pinesburg  Station  have  furnished  the 
few  fossils  so  far  discovered  in  this  bed. 

Fauna  of  the  Corynoides  Bed 

Climacograptus  putillus  (Hall) 

Climacograptus  spinifer  (Ruedemann) 

Corynoides  calicularis  Nicholson 

Leptobolus  inslgnis  Hall 

Schizocrania  filosa  (Hall) 

Cyclora  minuta  Hall 

CryptolitJius  tesselatus  Green 

Triarthrus  becki  Green 

Lepidocoleus  jamesi  (Hall  and  Whitfield) 

Caryocaris  silicula  n.  sp. 

Fossils  of  the  Eden  Division,  Martinsburg  Shale. — The  splendid  ex- 
posures of  the  lower  Cincinnatian  shales,  later  designated  the  Eden  shale, 
in  the  vicinity  of  Cincinnati,  Ohio,  have  afforded  a  wealth  of  excellently 
preserved  fossils  which  have  been  so  widely  studied  by  paleontologists  that 
a  large  described  fauna  has  resulted.  The  occurrence  of  this  same  fauna, 
well  enough  preserved  for  the  accurate  recognition  of  at  least  42  species, 
in  the  sandy  upper  portion  of  the  Martinsburg  shale  of  Pennsylvania, 
Maryland,  and  Virginia,  is  one  of  the  interesting  discoveries  of  recent 
years  in  Appalachian  geology. 

Numerous  exposures  of  this  sandy  upper  portion  of  the  Martinsburg 
shale  occur  along  the  Western  Maryland  Eailway  between  Williamsport 
and  Pinesburg  Station,  but  the  conditions  of  sedimentation  in  this  part 
of  the  valley  seem  to  have  been  unfavorable  for  life,  as  no  fossils  could  be 
found.  The  northward  and  southward  extensions  of  this  Martinsburg 
shale  belt  likewise  have  furnished  no  fossils,  but  the  shale  exposures  in 
the  mountains  to  the  west  exhibit  several  fossiliferous  zones.  In  Mary- 
land it  happens  that  no  good  exposures  of  the  upper  Martinsburg  occur 


168      THE  CAMBRIAN  AND  ORDOVICIAN  DEPOSITS  OF  MARYLAND 

along  the  roads  crossing  the  mountains,  and  here  the  fauna  is  known  only 
from  sandstone  debris  along  their  lower  slopes.  In  southern  Pennsyl- 
vania, on  the  contrary,  good  exposures  of  the  fossiliferous  strata  are  found 
along  several  turnpikes  crossing  the  mountains.  The  best  fossils  have 
been  procured  from  such  outcrops  along  Jordan  Knob,  one  and  a  half 
miles  northeast  of  Fort  Loudon,  Tuscarora  Mountain,  two  and  a  half 
miles  southeast  of  McConnellsburg,  and  Cowans  Gap,  five  miles  northeast 
of  McConnellsburg.  Two  fossiliferous  zones  are  known  in  the  Eden 
portion  of  the  Martinsburg  shale,  one  at  the  top  of  this  portion  and  the 
second  400  feet  lower.  The  faunas,  listed  on  next  page,  show  that  there 
is  little  difference  between  these  two  zones. 

Fossils  of  the  Maysville  Sandstone  Division,  Martinsburg  Shale. — As 
explained  on  a  previous  page  the  unfossiliferous  red  sandstones  and  shales 
immediately  overlying  the  Martinsburg  shale  have  been  distinguished 
and  mapped  in  southern  Pennsylvania  as  the  Juniata  formation.  Upon 
stratigraphic  grounds  these  red  beds  are  undoubtedly  the  equivalent  of 
the  Lower  or  Red  Medina  (Queenston)  shales  of  New  York.  Litho- 
logically  the  rocks  are  similar  and  in  each  area  they  are  underlaid  by 
strata  with  Cincinnatian  (Maysville)  fossils  and  followed  by  the  White 
Medina  (Tuscarora)  sandstone.  The  sandstone  underlying  the  Juniata 
formation  and  following  the  sandy  shales  of  Eden  age,  although  covering 
the  well-defined  Middle  Cincinnatian  (Maysville)  division  of  geological 
time  have  not  hitherto  been  separated  from  the  Martinsburg  shales  in 
Pennsylvania  and  Maryland.  As  their  area  of  occurrence  in  Maryland  is 
so  small  and  good  outcrops  are  almost  wanting,  the  practice  of  uniting 
these  strata  with  the  Martinsburg  shale  is  continued  in  this  volume. 

Exposures  along  the  turnpike  crossing  Tuscarora  Mountain,  one  and 
one-half  miles  southeast  of  McConnellsburg,  Pennsylvania,  have  afforded 
fairly  well-preserved  specimens  of  the  species  listed  below.  All  of  these 
fossils  occur  at  the  top  of  the  lower  division  of  these  sandstones  in  a  bed 
characterized  by  Orthorhynchula  linneyi.  This  Orthorhynchula  bed 
everywhere  marks  the  dividing  line  between  the  Lower  Maysville  (Fair- 


MARYLAND  GEOLOGICAL  SURVEY 


169 


LIST  OF  FOSSILS  IN  EDEN  PORTION  OF  MARTINSBURG  SHALE 


Jordan 
Knob,  Pa. 
(400  feet  be- 
low top) 


Jordan 

Knob,  Pa. 

(Top) 


Tuscarora 
Mt.  (400  feet 
below  top) 


Cowans 
Gap,  Pa. 


-  Climacograptus  bicornis  (Hall)  var * 

Diplograptus  vespertinus  (Ruedemann) . .  .         ;. 

-  Cornulites  flexuosus  (Hall) * 

1  Jleterocrinus  heterodactylus  Hall j        * 

Merocrinus  species  undetermined * 

Hudsonaster  clarki  n.  sp j 

Berenicea  vesiculosa  Ulrich 

Bythopora  arctipora  (Nicholson) * 

1  Hallopora  oneallisigillarioides(N\c,\\o\son)\        * 

1  Batostoma  jamesi  Nicholson * 

1  Arthropora  cleavelandi  (James) | 

1  Pholidops  cincinnatiensis  Hall i         * 

1  Dalmanella  multisecta  (Meek) ,         * 

-  Plectorthis  plicatella  Hall  var ! 

1  Strophomena  hallie  (S.  A.  Miller) 

1  Strophomena  sinuata  James  var 

1  Rafinesquina  squamula  (James) * 

-  Plectambonites  rugosnfi  (Meek) * 

1  Leptaena  gibbosa  (James) '.; 

-  Zygospira  modcsta  (Hall) j 

2  Ctenodonta  obliqua  Hall * 

1  Ctenodonta  filistriata  Ulrich 

2  Clidophorns  planulatns  (Conrad) 

1  Byssonychia  vera  Ulrich j 

1  Lyrodesma  conradi  Ulrich j 

"  Sinuitcs  cancellatus  (Hall) | 

2  Sinuites  granistriatus  (Ulricli) 

2  Tetranota  obsoleta  Ulrich i 

2  Hnrmotoma  gracilis   (Hall) * 

1  Lophospira  (Ruedemannia)  lirata  (Ulrich) 

2  Liospira  micula  (Hall) * 

1  Orthoceras  transvcrsum  Miller •      .'.". 

1  Cryptolithus  bellulutt  (Ulrich) * 

-  Cryptolithus  recurvus  (Uirich)  n.  sp j         * 

2  Triarthrus  becki  Green -. * 

1  Isotelus  stegops  Green ' 

1  Calymenc  granulosa  (Fuerste) * 

2  Aparchites  minutissimus  (Hall) * 

"  Ceratopsis  chambersi  (Miller) |         * 

-  Ulrichia  bivertex  (Ulrich) ; 

-  Bythocypris  cylindrica  (Hall) * 

-  Lepidocoleus  jamesi  (Hall  and  Whitfield) .         * 


1  Restricted  to  Eden.        "Occurs  in  Ed,n  and  other  formations. 


170      THE  CAMBRIAN  AND  ORDOVICIAN  DEPOSITS  OF  MARYLAND 

view)  and  the  Upper  Maysville  (McMillan)  divisions,  the  latter  in  the 
Appalachian  region  being  an  unfossiliferous,  gray  sandstone  apparently 
of  continental  origin  and  equivalent  to  the  Oswego  sandstone  of  the  New 
York  section. 

List  of  Maysville  Fossils  (Orthorhynchula  Bed),  Southern  Pennsylvania 

Lingula  nicTclesi  n.  sp. 
Plectorthis  plicatella  Hall 
Rafinesquina  alternata  (Emmons) 
Raflnesquina  squamula  (James) 
Orthorhynchula  linneyi  (James) 
Zygospira  modesta  (Hall) 
Zygospira  ?  erratica  (Hall) 
Ischyrodonta  unionoides  (Meek) 
Pterinea  (Caritodens)  demissa  (Conrad) 
Byssonychia  radiata  (Hall) 
Byssonychia  praecursa  Ulrich 
Allonychia  ovata  Ulrich 
Modiolopsis  modiolaris  (Conrad) 
Modiolodon  truncptus  (Hall) 
Orthodesma  nasutum  (Conrad) 
Liospira  micula  (Hall) 
Orthoceras  lamellosum  Hall 
Isotelus  megistos  Locke 

THE  JUNIATA  FORMATION 

Until  quite  recently  American  geologists  have  been  in  accord  in  regard- 
ing the  boundary  between  the  Ordovician  and  Silurian  systems  as  lying 
at  the  base  of  the  Bed  Medina.  Indeed,  by  many,  the  base  of  the  Silurian 
was  placed  still  lower,  namely,  at  the  bottom  of  the  Oneida  conglomerate 
which  was  supposed  to  underlie  the  Medina  and  to  be  equivalent  in  age 
to  the  Oswego  sandstone  which  actually  does  occur  under  the  Red  Medina. 
The  Oneida  conglomerate,  however,  has  been  proved  to  belong  at  the  top 
of  the  Medina  and  may  indeed  represent  the  initial  deposit  of  the  Clinton. 
The  Oswego  sandstone  therefore  became  a  valid  formation,  and  the  name 
Oswegan  series  was  coined  by  Clarke  and  Schuchert  to  include  the  Oswego 


MARYLAND  GEOLOGICAL  SURVEY 


CAMBRIAN  AND  ORDOVICIAN,  PLATE  XXIII 


FlG.  I. — VIEW  OF  MARTINSBURG  SHALE  TOPOGRAPHY,  LOOKING  NORTHEAST  FROM  A  POINT 
ONE-HALF  MILE  SOUTH  OF  WILSON,  MARYLAND.  CONOCOCHEAGUE  CREEK  IS  SEEN  IN  THE 
FOREGROUND  AND  THE  NATIONAL  HIGHWAY  IN  THE  MIDDLE. 


inc.  2. — VALLEY  OF  MARTINSBURG  SHALE  (BLAIR  VALLEY,  MARYLAND)  VIEWED  FROM  ROAD, 
JUST  WEST  OF  UNION  BETHEL  CHURCH.  THE  MOUNTAINS  ON  BOTH  SIDES  ARE  FORMED  OF 
THE  JUNIATA  AND  TUSCARORA  FORMATIONS. 


MARYLAND  GEOLOGICAL  SURVEY  171 

sandstone  and  the  Bed  and  White  Medina  formations  as  the  earliest  major 
division  of  the  Silurian.  The  reason  for  regarding  the  Oswego  sandstone 
as  Ordovician  in  age  has  been  given  on  a  preceding  page. 

In  the  standard  Ordovician-Silurian  section  of  New  York  the  last 
fauna  of  Ordovician  age  is  found  in  the  Pulaski  shale  where  species 
identical  with  Lower  Maysville  fossils  of  the  Cincinnatian  section  occur. 
Above  the  Pulaski  shale  are  unfossiliferous  gray  sandstones  (Oswego 
sandstone)  which  in  turn  are  succeeded  by  the  Lower  ("Red")  Medina 
forming  the  base  of  the  Silurian,  according  to  the  New  York  geologists. 
This  Lower  Medina  is  unfossiliferous,  but  in  the  overlying  Upper 
("White  ")  Medina  a  fauna  of  Silurian  types  is  preserved. 

In  Pennsylvania  and  Maryland  practically  the  same  section  is  de- 
veloped. The  sandstones  at  the  top  of  the  Martinsburg  shale  contain  the 
Pulaski  shale  representative  with  the  Lower  Maysville  fauna  and  above 
this  a  gray  unfossiliferous  sandstone  very  similar  to  the  Oswego  sand- 
stone occurs,  followed  in  turn  by  the  typical  Eed  Medina  here  termed  the 
Juniata  formation,  and  by  the  White  Medina  or  Tuscarora  sandstone. 

In  the  extremely  fossiliferous  Upper  Ordovician,  Cincinnatian  rocks 
of  the  Ohio  Valley,  the  equivalent  of  the  Pulaski  shale  of  New  York  is 
included  in  the  Lower  Maysville,  Fairview  formation.  This  is  succeeded 
by  the  fossiliferous  Upper  Maysville  (McMillan)  formation,  which  in  turn 
is  followed  by  the  equally  fossiliferous  Richmond  group.  Lately  it  has 
been  proved  by  actual  tracing  that  the  Richmond  group  passes  laterally 
into  the  Lower  (Red)  Medina  of  New  York.  Until  the  recent  researches 
of  Ulrich  upon  the  paleontology  and  stratigraphic  distribution  of  the 
Richmond  and  related  formations,  the  Upper  Ordovician  age  of  the  Rich- 
mond fauna  had  been  taken  for  granted.  In  his  paper  on  the  Ordovician- 
Silurian  boundary,  published  in  the  Proceedings  of  the  Twelfth  Session 
of  the  International  Geological  Congress,  Ulrich  has  reviewed  the  fauna! 
and  physical  aspects  of  the  data  relating  to  the  age  of  the  Richmond  group 
and  concludes  that  the  choice  of  the  Medina  including  the  Queenston- 
Richmond  formations  by  the  New  York  geologists  as  the  base  of  the 


172      THE  CAMBRIAN  AND  ORDOVICIAN  DEPOSITS  or  MARYLAND 

Silurian  has  strong  evidence  in  its  favor.  The  present  writer  has  had  the 
opportunity  of  studying  the  Richmond  group  over  a  large  portion  of  the 
United  States  with  the  result  that  in  previous  publications  he  has  classi- 
fied it  at  the  base  of  the  Silurian.  .  His  treatement  of  the  equivalent 
Juniata  formation  in  this  volume  under  the  Ordovician  is  not  due  to  a 
change  of  view,  but  to  the  fact  that  in  the  Silurian  volume  of  the  Mary- 
land Geological  Survey  the  base  of  the  Silurian  is  placed  at  the  Tuscarora 
sandstone.  As  the  Juniata  is  unfossiliferous  and,  moreover,  is  very  poorly 
exposed  in  Maryland,  further  details  are  believed  unnecessary  here, 
and  the  reader  is  referred  to  the  publication  by  Ulrich  cited  above  for 
more  data  as  to  its  age. 

In  Pennsylvania  and  Maryland  the  red  sandstone  and  shales  of  the 
Juniata  formation  form  the  upper  slope  of  the  mountains  just  west  of  the 
Great  Valley.  These  mountain  slopes  usually  show  only  reddish  sand- 
stone blocks  and  it  is  only  in  cliffs  or  in  road  sections  that  the  interbedded 
red  shales  can  be  seen.  The  sandstone  frequently  shows  cross  bedding  and 
sometimes  conglomerate  beds  of  white  quartz  or  red  jasper  boulders  or 
occasionally  red  shale  pebbles  are  developed.  The  occurrences  of  the 
formation  in  Maryland  consists  of  small  areas  on  Bear  Pond  Mountain, 
a  narrow  strip  on  Fairview  Mountain  and  another  narrow  strip  along  the 
eastern  side  of  Sword  Mountain.  None  of  these  areas  shows  a  section  of 
the  rocks  and  the  red  shales  and  sandstones  are  known  only  from  surface 
debris. 

The  relations  and  general  characters  of  the  Juniata  and  associated 
formations  are  well  shown  in  the  following  generalized  section  of  Upper 
Ordovician  and  Early  Silurian  strata  made  by  E.  0.  Ulrich  and  the 
writer.  This  section  is  exposed  along  the  west  slope  of  Tuscarora  Moun- 
tain between  McConnellsburg,  Pennsylvania,  and  the  summit  of  the 
mountain,  along  the  Mercersburg  pike  starting  about  a  mile  and  a  half 
southeast  of  McConnellsburg  and  continuing  southeast  and  south  for 
about  two  and  one-half  miles. 


MARYLAND  GEOLOGICAL  SURVEY  173 

Section  Along  West  Slope  of  Tuscarora  Mountain,  Southeast  of 
McConnellsburg,  Pennsylvania 

Silurian — Tuscarora  sandstone.  Feet 

Massive  granular  white  quartz  sandstone 200+ 

Ordovician  or  Silurian — Juniata  formation. 

Soft  red  unfossiliferous  sandstone  and  red  shale,  interbedded 400+ 

Ordovician-Martinsburg  shale. 

-  Oswego  gray  sandstone  member 150 

Maysville  (Fairview)  fossiliferous  gray  sandstone  (Orthorhynchula 

bed  at  top)   300 

Upper  Eden  shale  and  calcareous  sandstone  interbedded 400 

Middle  Eden  fossiliferous  shale  weathering  yellow 

Lower  Eden  shales,  not  exposed 

Trenton  and  Utica  ?  black  fissile  unfossiliferous  shale  with  black 

shale  at  base  bearing  graptolites 

Chambersburg  limestone 


174      THE  CAMBRIAN  AND  ORDOVICIAN  DEPOSITS  OF  MARYLAND 


.3 

4 

1 

1 

1 
2 
I 

1 
2 
1 

4 

5 

a 

7 
8 
1 

Id 
11 

1 
2 

3 
4 
5 
G 

7 

1 
2 
I 

4 

6 

6 

7 
8 

9 

10 
11 
12 
13 

Note: 
1  =  Stonehenge   Member 
2  =  Cryptozoon  steeli  Bed 
3  =  Ceratopea  Bed 
4  =  Turritoma  Bed 
5  =  Greencastle  Bed 
6  =  Caryocystites  Bed 
7  =  Tetradium  Bed 
8  =  Echinospherites  Bed 
9  —  Nidulites  Bed 

CAMBRIAN 

ORDO- 
VICIAN 

WAUCOBAN 

vvavnesDoro  i'orm  |  Aca- 
Elhrook  Limestone  i  dian 

OZARKIAN 

CANADIAN 

£ 
7. 

e 

1 

8 

T 

K 

0) 
rr  T" 

Antietam  Sandstone 

Tomstown  Limestone 

Conococheague 
Limestone 

Beekmantown 
Limestone 

10  —  Christiania  Bed 
11  =  Eden   Division 
12  =  Sinuites  Bed 
13  =  Corynoides  Bed 
14  —  Fairview  Division 

' 
SPECIES 

c 

1 
2 

0 

"a 

"c 

1 

t 

|j 

es  Mills 
Smithsbursr 

Waynesboro,  Pa. 

Wavnesboro,  Pa. 

g 

p 

Antietam  Station 

Eunkstown 

Chambersbure  Quad. 

o 

> 

1 

'c 
> 

I 

O 

•c 

1 

o 

o 

g 

1 

1 

wear  mgerstown 
Near  Funkstown 

Williamsport 

Near  Charlton 

-U 

I 

Chambersburg  Quad. 

^ 

i^ 

3* 

12 

11 

#.   rt   o! 
es  o   <u 

ri    ~ 

c   c- 

<  y. 

III 

THALLOPHYTA.     Algae 
Cryptozoon  proliferum  Hall    

4r 

1 

Cryptozoon  undulatum  Bassler  n.  sp  

* 

* 

• 

Cryptozoon  steeli  Seely    

0 

Pakeophycus  tubulare  Hall  , 

i 

1  •• 

Solenopora  compacta   (Billings)    

Nidulites  pyriformis  Bassler    

Receptaculites   occidentalis   Salter    . 

POKIFERA.     Spongiae 

2 

•2 

Camarocladia  rugosa  Ulrich  

Hindia  parva  Ulrich   

COELENTERATA.     Anthozoa 

• 

COELENTERATA.     Graptolitoidea 

ECHINODEKMATA.     Cystoidea 

ECHINODERMATA.     Crinoidea 

ECHINODERMATA.     Stelleroidea 
Hudsonaster  clarki  Bassler  n.  sp  

MOLLUSCOIDEA.     Bryozoa 

Batostoma  jamesi  Nicholson    • 

Bythopora  arctipora   (Nicholson)    

Escharopora  confluens  Ulrich    

! 

MARYLAND  GEOLOGICAL  SURVEY 


175 


ORDOVICIAN 

CANADIAN 

f 

CHAZYAN 

MOHAWKIAN    AND   ClNCINNATIAN 

Beekmantown 
Limestone 

. 
.  .; 

Frederick  Limestone 

Stones  River 
Limestone 

Ohambersburg 
Limestone 

Martinsburg 
Shale 

Mercersburg  Quad. 

Canada 

Vermont 

1 

•f 

0 

I 

% 

Virginia 

East  of  Frederick 

5 
j 
3 

a 

\ 

j  » 

H      ^ 

Near  Maugansville 
Chambersburg  Quad. 

Canada 

i 
•g 

s 

' 

I 

X  ': 

\ 
\ 
i 

I! 

H  :£ 

Chambersburg  Quad. 

Mercersburg  Quad. 

1 

OJ 

I 

.* 

.a 

| 

^ 

Virginia 

c 

Kentucky 

Tennessee 

o 

z. 

j 

Canada 

Esthonia,  Russia 

! 

H   5 
11 

t   K 

Fairview  Mt. 

•e 

c 

1 

Mercersburg  Quad. 

Chambersburg  Quad. 

5 

V 

fc 

Virginia 

15 
c 

Kentucky 

Tennessee 

Missouri 

c 
1 
It 

1 

a 

B 

•a 

1 

8 

4     ') 

ft 

8 

a 

8 

7 

7 

7 

12 

12 

•• 

12 

12 

12 

12 

fi 

7 

* 

0 

7 

7 

9 

IS 

? 

1 

11 

11 

1 

3 

19 

j 

19 

1 

3   8 

« 

i 

I 

(5 

11 

1 

n 

11 

11 

n 

n 

g 

n 

7 

7 

I 

g 

9 

q 

a 

f) 

s 

•! 

g 

n 

1  1 

1 

11 

11 

n 

1 

n 

1  1 

ff 

6 

•  •   1 

12 


176 


14 
15 

16 
17 
18 
19 
20 

21 
22 
23 

24 
25 
26 
27 
28 
2!) 
30 
31 
32 
33 
34 
35 
36 
37 

as 

3!) 
40 
41 
42 
43 
44 
45 
46 
47 
48 
4fl 
50 
51 
52 
53 
54 
55 
56 
57 
58 
5!) 
60 
61 

Note: 
1  •=.  Stonehenge   Member 
2  =  Cryptozoon  steeli  Bed 
3  =  Ceratopea  Bed 
4  :=  Turritoma  Bed 
5=Greencastle  Bed 
6  =  Caryocystites  Bed 
7  =  Tetradium  Bed 
8  =r  Echinospherites  Bed 
9  —  Nidulites  Bed 

CAMBRIAN 

ORDO- 
VICIAN 

WAUCOBAN 

,   c 

01  .2 

OZARKIAN 

CANADIAN 

Harpers  Shale 

Antietam  Sandstone 

Tomstown  Limestone 

Wavnesboro,  Pa.  1  Waynesboro  Form 

Wavnesboro,  Pa.  1  Elbrook  Limestone 

Conococheague 
Limestone 

Beekmantown 
Limestone 

10=Christiania  Bed 
11=:  Eden   Division 
12  =  Sinuites  Bed 
13  =  Corynoides  Bed 
14  =  Fairview  Division 

SPECIES 

v. 

i 

i 

"3. 

2 

V 

3 

V 

•B 

= 

5 

I 

i 

•c 
i 

O 
S 

Bf| 

3    b 

X>;  a, 
cgx: 

t 
I 

Wavnesboro,  Pa. 

§ 

•s 

Antietam  Station 

c 

1 
•a 

£ 

<§ 

1 
5 

£ 

.2 

c 
•c 

CS 

Mexico 

Hagerstown 

j 

I 

Chariton 

X 

"C 

I 

1 

•e 

H£ 

"d 

K 

>-    E| 
?  _;  /  C 

W  2:^ 

£ 

d 

OJ 

^ 

d 

rt   o!1  « 

4)     0>  J3 

Jz;  fco 

•f 

.b4S 
>  & 

3,  & 

g 

cd  ;^-    d   ^  w 

*PWwp 

MOLLUSCOIDEA.      Bryozoa.  —  Continued 

MOLLUSCOIDEA.     Brachiopoda 

Lingula  ricinijormis   Hall    :  

Lingula  nicklesi  Bassler  n.  sp  

v 

V  " 

* 

* 

Yebertella  vulgaris  Raymond    

Webertella   bellarugosa   (Conrad)    

;.j 

8 

8 

1 

i 

Strophomena  stosei  Bassler  n    sp   .        . 

Plectafnbonites  rugosus   (Meek)  

Leptaena  gibbosa    (James)    

Leptaena   tenuistriata   Sowerby  var  

Rafinesquina   champlainensis  Raymond    

• 

Rafinesquina   alternata    (Emmons)  

1 

MARYLAND  GEOLOGICAL  SURVEY 


177 


ORDOVICIAN 

CANADIAN 

? 

CHAZYAN 

MOHAWKIAN    AND   ClNCINNATIAN 

Beekmantown 
Limestone 

Frederick  Limestone 

Stones  River 
Limestone 

Chambersburg 
Limestone 

Martinsburg 
Shale 

Mercersburg  Quad. 

Canada 

Vermont 

.M 

0 

I 

•- 

V 

Virginia 

East  of  Frederick 

3 

00 

j 

| 

Near  Maugansville 

Chambersburg  Quad. 

Canada 

~ 

Pinesburg  Station 

Wilson 

Chambersburg  Quad. 

Mercersburg  Quad. 

fe 

X 

f- 

* 

'•£ 

'3 
1 

1 

Virginia 

.2 
0 

Kentucky 

Tennessee 

Wisconsin 

Minnesota 

Canada 

Esthonia,  Russia 

! 

o 

1 
* 

Rickard  Mt 

Fairview  Mt. 

Williamsport 

Mercersburg  Quad. 

Chambersburg  Quad. 

•g 

hO 

1 

Virginia 

c 
2 
C 

Kentucky 

Tennessee 

Missouri 

Wisconsin 

Minnesota 

| 

10 

10 

10 

10 

10 

1  1 

1  1 

i; 

t\ 

6 

G 

f, 

p 

8  .. 

S 

8  -- 

g 

g 

s 

8 

8 

12 

!•> 

is 

..US 

is 

1? 

13 
12 

12 

12 

12 

12 

11 

10 

10 

10 

10 

10 

10 

1-2 

12 

12 

1" 

1  1 

11 

i 

* 

n 

a 

* 

r, 

<•> 

r; 

14 

11 

1  1 

T> 

1° 

12 

11 

11  '-- 

3 

3 

•} 

1 

\ 

s 

8 

8 

R 

8 

g 

w 

g 

1° 

11 

n 

10 

10 

10 

10 

n 

11 

10 

10 

10 

10 

i° 

I9 

1° 

g 

11 

IS 

6 

(i 

g 

(i 

8 

a 

8 

8 

8 

8 

11 

n 

.. 

u 

1 

178      THE  CAMBRIAN  AND  ORDOVICIAN  DEPOSITS  OF  MARYLAND 


f.2 

6H 
64 
65 
66 
67 
68 
6!) 
70 
71 
72 

1 
2 

1 

2 
3 
4 

5 

g 

7 

8 
9 
10 
11 
12 

ia 

14 

15 
16 
17 

18 
1!) 
20 
21 
22 
23 
24 
25 
26 
27 
28 
2!) 
30 
31 

Note: 
1  =  Stonehenge   Member 
2  =  Cryptozoon  steeli  Bed 
3  =  Ceratopea  Bed 
4  —  Turritoma  Bed 
5  =  Greencastle  Bed 
6  —  Caryocystites  Bed 
7  =  Tetradium  Bed 
8  =  Echinospherites  Bed 
9  —  Nidulites  Bed 
10=Christiania  Bed 
11  =  Eden   Division 
12  =  Sinuites  Bed 
13  =  Corynoides  Bed 
1  4  r=  Fairview  Division 

SPECIES 

CAMBRIAN 

ORDO- 
VICIAN 

WAUCOBAN 

,     C 

g.2 
<*° 

OZARKIAN 

CANADIAN 

Harpers  Shale 

Antietam  Sandstone 

Tomstown  Limestone 

\Vavnesboro  Form 

Klbrook  Liniestono 

Conococheague 
Limestone 

Beekmantown 
Limestone 

5 
i 

i 
« 

1 

K 

V 

~ 

s 

c 

•^ 
=:' 

1 

£ 

0 

ifc 

<f  -a 
£  '£ 
a 

*  b,' 

W^ 

Little  Antietam  Cr. 

Sniithsburg 

Chambersburg  Quad. 

Eakles  Mills 

Near  Smithsburg 

Near  Wavnesboro,  Pa. 

Near  Wavnesboro,  Pa. 

\f\ir  Wavnesboro,  Pa. 

u 

'B 

£. 

| 

1 
r. 

Near  Antietam  Station 
Near  Funkstown 
Chambersburg  Quad. 

M 

^ 
C 
fH 

»5 

Virginia 

tt 

2 
g 

Colorado 

New  Mexico 

Near  Hagerstown 

Near  Funkstown 

Williamsport 

Near  Charlton 

Huyett 
Chambersburg  Quad. 

MOLLUSCOIDEA.     Brachiopoda.  —  Continued 

.. 

» 

•' 

VERMES.     Tubicola 
Cornulites  fiexuosus  (Hall) 

* 

t 

i 

MOLLUSCA.     Pelecypoda 

Ctenodonta  obligua   (Hall) 

Byssonychia  vera  (Ulrich)   

Byssonychia  radiata  (Hall)    

1 

Allonychia  ovata  Ulrich   

Pterinea  (Caritodens)   demissa   (Conrad)    

Lyrodesma  conradi  Ulrich   

Modiolopsis  modiolaris   (Conrad)    

Modiolodon   truncatus   (Hall)    

Orthodesma  nasutum  (Conrad)    

MOLLUSCA.     Gastropoda 
PleuTotoinaria,  f  canadensis  Billings  

S 

Pleurotomaria    f   gregaria   Billings  

4.. 

1 

1 

i 

3 

4   4 

4   4 

•-' 

•' 

f 

s 

Maclurites  oceanus  (Billings)    

4.. 

•: 

i 

1 

MARYLAND  GEOLOGICAL  SURVEY 


179 


ORDOVICIAN 

CANADIAN 

? 

CHAZYAN 

MOHAWKIAN    AND   ClNCINNATIAN 

Beekmantown 
Limestone 

Frederick  Limestone 

Stones  River 
Limestone 

Chambersburg 
Limestone 

Martinsburg 
Shale 

Mercersburg  Quad. 

g 

1 

Vermont 

| 

X 

1 
X 

Virginia 

East  of  Frederick 

Pinesburg  Station 

Wilson 

Near  Maugansville 

Chambersburg  Quad. 

Canada 

hO 

£ 
X 

Pinesburg  Station 

. 

Chambersburg  Quad. 

Mercersburg  Quad. 

I 

E 

3 

I 

.2 
f 

£ 

'f- 

Virginia 

.2 

5 

Kentucky 

Tennessee 

I 

Wisconsin 

Minnesota 

Canada 

Esthonia,  Russia 

c 

•o 

i 

Fairview  Mt. 

Williamsport 

•c 

,Q 
1 

Chambersburg  Quad. 

| 
fc 

Virginia 

C 

Kentucky 

Tennessee 

Missouri 

Wisconsin 

Minnesota 

1 

n 

i! 

<i 

'i 

,, 

'i 

1° 

12 

10 

10 

t; 

10 

10 

11 

14 

14 

14 

14 

7 

7 

10 

in 

11 

11 

14 

'1 

7 

11 

n 

11 

1  1 

11 

11 

14 

14 

14 

14 
1 

11 

n 

14 

II 

14 

14 

14 

14 

11 

14 

14 

14 

14 

14  ] 
1 

11 

n 

14 

14 

14 

14 

14 

•  i    1 

3 
4 

•) 

1 

1 

1 

3 

1 

11 

II 

1 

• 

4 

..   2 

1  1 

11 

..   l 
• 

i 

n 

11 

• 

0 

o 

" 

. 

, 

» 

tt 

" 

9 

3 

i 

..   ..! 

0 

4 

i 

• 

' 

0 

7 

7 

7 

Q 

7 

7 

- 

1 

1 

180      THE  CAMBRIAN  AND  ORDOVICIAN  DEPOSITS  OF  MARYLAND 


32 
33 
34 
35 
36 
37 
38 
39 
40 
41 
42 
43 
44 
45 
46 
47 
48 
4!) 
50 
5! 
52 
53 
54 
55 
56 

57 
58 
5!> 
6( 
61 
62 
63 
64 
65 
66 
67 
68 
6! 
70 
71 
72 

I 

4 
1 

i 
'   1 

Note: 
1  =  Stonehenge   Member 
2  :=  Cryptozoon  steeli  Bed 
3  —  Ceratopea  Bed 
4  =  Turritoma  Bed 
5  =  Greencastle  Bed 
6  =  Caryoeystites  Bed 
7  =  Tetradium  Bed 
8  =  Echinospherites  Bed 
9  =  Nidulites  Bed 
lO^Christiania  Bed 
11  =  Eden   Division 
12  =  Sinuites  Bed 
13  =  Corynoides  Bed 
14:=  Fairview   Division 

SPECIES 

CAMBRIAN 

ORDO- 
VICIAN 

WAUCOBAN 

,  c 

T-.    c- 

o~ 

•*,  - 

OZARKIAN 

CANADIAN 

Harpers  Shale 

Antietam  Sandstone 

Tomstown  Limestone 

Near  Wavnesboro,  Pa.  1  Waynesboro  Form 

VP-JT  W-iviiPKhnrn  To  l-'ll,r,,,.L  1  iiin-  Inn, 

Conococheague 
Limestone 

• 

Beekmantown 
Limestone 

a 
i 

oi 

i 

a 

3 

TT 

5 

C 

S 
0 

"H 
£ 

_w 
S 
E 

3 

s 

V 

% 

2 

4) 

s 

OJ 

-3 

l> 

Little  Antietam  Cr. 

Smithsbufg 
Ohatiibersbur^  Qund. 

Eakles  Mills 

Near  Smithsburg 

Near  Wavnesboro,  Pa. 

Sharosburg 
Near  Antietam  Station 
Near  Funkstown 

Chambersburg  Quad. 

•£ 

0 

P* 

1 
X 

a 

z 
5> 

M 

Colorado 

Near  Hagerstown 

1  Near  Funkstown 

1 
^ 

t 

|  Near  Charlton 

Huyett 
Chambersburg  Quad. 

MOLLUSCA.     Gastropoda.  —  Continued 

4   4 

1 

1 

I 

1 

I 

1 

.  ..j  

2 
1 

2 
1 

2 

i 

..    2 

1 

1 

1 

..    3 

f      t   I'f              't'rf    ]        CITlr'   hi            '              ' 

| 

1 

I 

* 

Conularia  trentonensis  Hall  

MOLLUSCA.       Cephalopoda 

1 

4   4 

Gonioceras  chaziense  Ruedemann  

Ooceras    kirbyi    (Whitfield)     

1 

1 

Cyrtoceras  gracile  Cleland  

1 

1 

Cyrtocerina   mercurius   Billings    

4   4 

Cyclostomiceras  cassinense  (Whitfield)  ?  

1 

ARTHROPODA.     Crustacea 
Eoharpes  ottawaensis  (Billings)    

Cryptolithus  tesselatus  Green   

MARYLAND  GEOLOGICAL  SURVEY 


181 


ORDOVICIAN 

CANADIAN 

East  of  Frederick  i  Frederick  Limestone 

CHAZYAN 

MOHAWKIAN    AND   ClNCINNATIAN 

Beekmantown 
Limestone 

Stones  River 
Limestone 

Chambersburg 
Limestone 

Martinsburg 
Shale 

Meroersburg  Quad. 

1 
O 

Vermont 

•a 

5 

£ 

4J 
•f- 

.2 

hi 

Pinesburg  Station 

I 

5 
I 
| 

5 

Chambersburg  Quad. 

Canada 

1 

(H 

0 

| 

:f 

1  1 
H  ^ 

Chambersburg  Quad. 

Mercersbunr  Quad. 

^ 

i 

t- 

i 

'H 

'S 

1 

Virginia 

-S 

C 

Kentucky 

Tennessee 

g 

c 

Wisconsin 

Minnesota 

c 

a 
a 

C 

Esthonia,  Russia 
Washingrton  Countv 

Rickard  Mt. 
Fairview  Mt. 

William  sport 

Mercersburg  Quad. 

Chambersbure  Quad. 

1 

0 

1 

O 

0 

Kentucky 

Tennessee 

Missouri 

Wisconsin 

Minnesota 

Canada 

! 

l 

1 

2 

T 

1 

1" 

is 

1 

7 

7 

7 

1 

^ 

2 

1'' 

•> 

2 

. 

11 

'• 

H 

1 

i 

11 

9 

1° 

12 

12 

i  •> 

2 

9 

2  -- 

9 

9 

i 

2 

12 

2 

5 

5 

9 

19 

1  .. 

1 

-11 

1 

.14 

2  19 

, 

•> 

1° 

1" 

6  .  . 

i; 

1 

2 

, 

f, 

T 

1 

•• 

. 

9 

1" 

1 

11 

1 

2 

- 

•i 

0 

0 

1  J 

1 

182      THE  CAMBRIAN  AND  ORDOVICIAN  DEPOSITS  OF  MARYLAND 


6 
7 

8 
9 
10 
11 
12 
13 
14 
15 
Hi 
17 
18 
1!) 
20 

21 

22 

28 

24 
25 
2l> 
27 
2S 
29 
3(1 
31 

82 
88 

34 
35 

37 

38 

40 
41 

42 

43 
44 

45 

Note: 
1  =  Stonehenge   Member 
2  =  Cryptozoon  steeli  Bed 
3  =  Ceratopea  Bed 
4  =  Turritoma  Bed 
5  =  Greencastle  Bed 
6  —  Caryocystites  Bed 
7  =  Tetradium  Bed 
8  =  Echinospherites  Bed 
9  —  Nidulites  Bed 

CAMBRIAN 

ORDO- 

VICIAN 

WAUCOBAN 

,  c 

^.2 

OZARKIAN 

CANADIAN 

Harpers  Shale 

Antietam  Sandstone 

Tomstown  Limestone 

Waynesboro  Form 

Elbrook  Limestone 

Conococheague 
Limestone 

Beekmantown 
Limestone 

10  —  Christiania  Bed 
11  =  Eden   Division 
12  =  Sinuites  Bed 
13  =  Corynoides   Bed 
14  =  Fairview  Division 

SPECIES 

00 

5 

H 

i 

X 

0) 

K 
a, 

^5 

" 

Eakles  Mills 

1 

5 

K 

.s 

Little  Antietam  Cr. 
Smithsburg 

t'hambersburg  Quad. 

Eakles  Mills 

Near  Smithsburg 

Near  Wavnesboro,  Pa. 

Near  Waynesboro,  Pa. 

Near  Wavnesboro,  Pa. 

Sharosburg 

Near  Antietam  Station 

Near  Funkstown 

Chambersburg  Quad. 

E 

c 

t 

y. 

| 

;> 

i 

t 

Colorado 

New  Mexico 

Near  Hagerstown 

Near  Funkstown 

Wiliiamsport 

Near  Charlton 

Huyett 
Chambersburg  Quad. 

ARTHROPODA.     Crustacea.  —  Continued 
Ampyx  (Lonchodomas)  halli  Billings  

Dolichometopus  sp  

v 

1  * 

',' 

V 

'-> 

2 

,-,**  .                 ,   .       cH-ir       \      

2 

T   'ji   th  •        H  •  1  '    '    R'lT   e 

1 

I     t  1                    t        T  Ofkp 

1 

1 

1 

1 

, 

,. 

Acidaspis  ulrichi  Bassler  n.  sp  

Ceraurua  pleurexanthemus  Green    

" 

Pliomerops  salteri   (Billings)    

3 

AimmopoDA.     Branchiopoda 

.. 

ARTHROPODA.     Ostracoda 
Isochilina   (jregaria    (Whitfield)               .    .    . 

3 

9 

Isochilina   seelyi    (Whitfield)     

4.. 

Leperditia  fabulites   (Conrad) 

Leperditella   tiimida    (Ulrich)    

Aparchites   mirtutissimus    (Hall)     

Drepanella   macra  Ulrich    

M  acronotella    ulrichi    Ruedemann     

Ceratop'iis    chambersi    (Miller) 

Ulrichia     bivertex     (Ulrich)      

1 

Bythomipris   ct/lindrica    (Hall)    

Lepidocoleus  jamesi  (Hall  &  Whitfield)   ,.  . 

j 

MALACOSTRACA 
Caryocaris  siticula  Bassler  n.  sp  

1 

MARYLAND  GEOLOGICAL  SURVEY 


183 


ORDOVICIAN 

CANADIAN 

Frederick  Limestone  1  •* 

CHAZYAN 

MOHAWKIAN    AND   ClNCINNATIAN 

Beekmantown 
Limestone 

Stones  River 
Limestone 

Ohambersburg 
Limestone 

Martinsburg 
Shale 

Mercersburg  Quad. 

Canada 

Vermont 

0 

5 

£ 
fe 

Virginia 

East  of  Frederick 

Pinesburg  Station 

Wilson 

Near  Maugansville 

Chambersburg  Quad. 

Canada 

5 
>• 

Pinesburg  Station 

''f 

Chambersburg  Quad. 

Mercersburg  Quad. 

Z 

£ 

'^ 

1 

Virginia  * 

c 

i 

Kentucky 

Tennessee 

te 
t 

Wisconsin 

Minnesota 

Canada 

Esthonia,  Russia 

Washington  County 

Rickard  Mt. 

Fairview  Mt. 
Williamsport 

Mercersburg  Quad. 
Chambersburg  Quad. 

if 
5 

Virginia 

C 

Kentucky 

Tennessee 

Missouri 

Wisconsin 

Minnesota 

Canada 

* 

. 

• 

. 

1 

2 

2 

2 

2 

i 

' 

" 

12  ..   .. 

11 

12  11  12 
..  11  .. 

..14 

14:     

14 

* 

1 

1 

i 

0 

9    9 

9 

L2 

'- 

12 

1" 

i 

i 

. 

12 

i 

12 

12 

12 

12 

i 

* 

1  1 

11 

jj 

12 

12 

fl 

c 

.    fi 

i 

4 

1 

4 

i 

> 

7 

n 

11 

7 

n 

11 

1  1 

11 

n 

1  1 

1" 

11 

13 

!     1 

SYSTEMATIC  PALEONTOLOGY 

OF 

THE  CAMBRIAN  AND  ORDOVICIAN 
DEPOSITS  OF  MARYLAND 

BY 

R.  S.  BASSLER 


SYSTEMATIC  PALEONTOLOGY 
CAMBRIAN  AND  ORDOVICIAN 

THALLOPHYTA R.  S.  BASSLER. 

PORIFERA  R.  S.  BASSLER. 

COELENTERATA  .. . . R.  S.  BASSLER. 

ECHINODERMATA  R.  S.  BASSLER. 

VERMES   R.  S.  BASSLER. 

MOLLUSCOIDEA R.  S.  BASSLER. 

MOLLUSCA R.  S.  BASSLER. 

ARTHROPODA  .  ..R,  S.  BASSLER. 


THALLOPHYTA 

CLASS  ALGAE 

Genus  GRYPTOZOON  Hall 

CRYPTOZOON  PROLIFERUM  Hall  * 

Plate  XXVIII,  Figs.  1,  2;  Plate  XXIX,  Fig.  1 

Cryptozoon  proliferum  Hall,  1884,  36th  Rept.  New  York  State  Mus.  Nat. 

Hist.,  pi.  vi. 
Cryptozoon  proliferum  Walcott,  1912,  Smithsonian  Misc.  Coll.  57,  p.  258, 

pi.  xxxvii,  figs.  1-3. 

Description. — "  These  bodies  are  made  up  of  irregular,  concentric 
laminae  of  greater  or  less  density  and  of  very  unequal  thickness.  The 
substance  between  the  concentric  lines,  in  well-preserved  specimens,  is 
traversed  by  numerous,  minute,  irregular  canaliculi  which  branch  and 
anastomose  without  regularity.  The  central  portions  of  the  masses  are 
usually  filled  with  crystalline,  granular,  and  oolitic  material  and  many 
specimens  show  the  intrusion  of  these  extraneous  and  inorganic  sub- 
stances between  the  concentric  laminae.  That  these  are  intrusions,  and 
not  inclusions,  is  shown  from  the  fact  that  they  can  be  traced  to  a  vertical 
fissure  or  break  leading  to  the  exterior  of  the  fossil  and  which  allowed  the 
crystalline  matter  to  enter." — Hall,  1884. 

As  noted  under  the  following  species,  Cryptozoon  proliferum  is  char- 
acterized by  its  growth  from  a  widely  expanded,  almost  flat,  series  of 
lamellae  into  confluent  heads  of  a  size  varying  from  four  or  more  inches 
in  diameter  at  the  center  of  a  growth  to  small,  concentric  areas  an  inch  or 
less  wide  on  the  edge. 

*  In  the  specific  bibliography  throughout  this  volume  only  the  original  and 
the  more  important  subsequent  references  are  cited.  The  complete  bibli- 
ography for  the  Post-Cambrian  forms  may  be  consulted  in  the  Bibliographic 
Index  of  American  Ordovician  and  Silurian  fossils  published  as  Bulletin  92, 
U.  S.  National  Museum. 


190  SYSTEMATIC  PALEONTOLOGY 

Occurrence. — CONOCOC-HEAGUE  LIMESTONE. — In  Pennsylvania,  Mary- 
land, and  Virginia  this  is  a  characteristic  fossil  at  the  hase  of  the  Conoco- 
cheague  limestone.  Specimens  may  be  found  at  practically  all  of  the 
normal  contacts  between  the  Elbrook  and  Conococheague  limestones.  The 
species  is  particularly  abundant  in  the  vicinity  of  Sharpsburg,  Maryland, 
and  also  in  a  cut  of  the  Norfolk  and  Western  Bailroad,  one  mile  south- 
west of  Antietam  Station  where  a  reef  of  these  algae  is  exposed. 

The  original  types  came  from  the  Ozarkian  (Hoyt)  limestone  of  Sara- 
toga County,  New  York. 

Collections. — Maryland  Geological  Survey,  TJ.  S.  National  Museum. 

CRYPTOZOON  UNDULATUM  n.  sp. 
Plate  XXIX,  Figs.  2,  3;  Plate  XXX 

Description. — The  Conococheague  limestone  in  the  Appalachian  Valley 
from  Virginia  to  northeastern  Pennsylvania  and  the  corresponding  strata 
in  New  York  State  afford  a  second  well-defined  species  of  Cryptozoon 
which  occurs  in  association  with  C.  proliferum.  Comparison  of  the  two 
species  will  bring  out  the  essential  characters  of  the  present  new  one. 
Cryptozoon  proliferum  grows  from  a  widely  expanded  almost  flat  series 
of  lamellae  into  numerous  confluent  heads  of  unequal  size.  In  C.'undu- 
latum  the  laminae  are  at  first  evenly  undulating,  forming  in  edge  view,  a 
pseudo-columnar  structure,  the  columns  averaging  20  mm.  in  width. 
A  cross-section  through  this  part  of  the  fossil  shows  these  column-like 
areas  to  be  of  equal  size  and  totally  unlike  the  corresponding  portion  of 
C.  proliferum.  Following  the  undulating  zone  in  C.  undulatum  the 
laminae  go  through  a  stage  in  which  the  distinct  lamination  disappears. 
Then,  with  a  new  growth,  the  characteristic  undulations  of  the  species 
reappear. 

Occurrence. — CONOCOCHEAGUE  LIMESTONE.  Associated  with  Crypto- 
zoon proliferum.  The  types  are  from  a  locality  two  and  one-half  miles 
southeast  of  Funkstown,  Maryland,  where  examples  were  numerous. 
Sharpsburg  and  vicinity  also  show  numerous  specimens,  particularly  in 
the  stone  fences.  This  species  and  C.  proliferum  have  also  been  found 


MARYLAND  -GEOLOGICAL  SURVEY  19.1 

in  the  Conococheague  limestone  as  far  north  as  the  Eeading  area  of 
Pennsylvania.  They  both  occur  in  the  Hoyt  limestone  near  Saratoga 
Springs,  New  York. 

Collections. — Maryland  Geological  Survey,  U.  S.  National  Museum. 

CRYPTOZOON  STEELI  Seely 

Plate  XXXIV,  Fig.  1 

Cryptozoon  steeli  Seely,  1906,  Kept.  State  Geol.  Vermont,  vol.  v,  p.   161, 
pis.  xxxiv,  xxxvi,  xliii,  fig.  1. 

Description. — The  Beekmantown  rocks  of  New  York,  Vermont^  and 
northward  into  Canada  contain  a  species  of  Cryptozoon  several  inches  to 
a  foot  in  diameter  which  differs  from  the  other  species  of  the  genus  in 
that  the  organism  is  usually  made  up  of  a  single  globular  or  hemispherical 
mass  of  lamellae.  The  successive  layers  are  quite  parallel  and  arranged 
concentrically  even  in  the  largest  specimens.  These  layers  are  composed 
of  a  dense  material  apparently  without  definite  organic  structure. 

In  the  Cumberland  Valley  this  particular  form  of  Cryptozoon  is 
apparently  restricted  to  a  definite  zone  in  the  Lower  Beekmantown.  As 
the  fossil  weathers  out  in  large,  silicified  masses  accompanied  by  much 
platy  chert,  this  zone  is  generally  easily  recognized.  Cryptozoon  steeli 
therefore  forms  an  excellent  guide  fossil  in  mapping,  as  it  not  only 
assists  in  the  recognition  of  the  strata,  but  the  chert  masses  accompanying 
it  indicate  the  outcrops  of  this  zone.  These,  if  plotted,  help  to  decipher 
the  geological  structure.  The  Cryptozoon  steeli  zone  of  chert  has  been  a 
most  valuable  aid  in  determining  the  structure  of  the  Beekmantown  in 
the  Valley  west  of  the  Martinsburg  shale  belt  where  frequently  lack  of 
rock  outcrops  has  caused  great  difficulty  in  mapping. 

Occurrence. — BEEKMANTOWN  LIMESTONE  (Cryptozoon  steeli  zone). 
In  the  Appalachian  Valley  of  Maryland  and  southern  Pennsylvania 
this  is  a  cbmmon  fossil  about  800  feet  above  the  base  of  the  Beekmantown. 
Numerous  specimens  may  be  found  among  the  residual  cherts  of  this 
zone  at  practically  every  outcrop  both  east  and  west  of  the  Martinsburg 
shale  belt  of  Maryland,  particularly  in  the  vicinity  of  Hagerstown. 

Collections. — Maryland  Geological  Survey,  U.  S.  National  Museum. 
13 


192  SYSTEMATIC  PALEONTOLOGY 

Genus  PALyEOPHYCUS  Hall 

PALJEOPHYCUS  TUBULAEE  Hall 

Plate  XXXI,  Fig.  1 

Palceophycus  tubulare  Hall,  1847,  Pal.  New  York,  vol.  i,  p.  7,  pi.  ii,  figs.  1, 
2,  4,  5. 

Description. — Although  formerly  considered  as  seaweeds,  the  fossil 
remains  described  under  this  name,  and  related  so-called  genera  and 
species,  are  of  very  doubtful  origin.  The  particular  form  here  illustrated 
is  interesting  because  it  occurs  in  such  widely  separated  areas,  although 
the  two  formations  in  which  it  is  found  are  believed  to  be  of  the  same 
age.  The  specimens  as  observed  on  weathered  surfaces  consist  of  un- 
evenly bent  or  flexuose  cylindrical  stems  sometimes  gradually  tapering 
to  a  point,  irregularly  branched  and  often  bifurcated.  In  Maryland,  as 
in  New  York,  these  stems  when  weathered  appear  as  if  hollow.  The 
stems  and  branches  are  usually  much  compressed,  smooth,  and  preserve 
no  traces  of  structure. 

Occurrence. — BEKKMANTOWN  LTMESTONF  (Stonehenge  member).  Sev- 
eral localities  in  the  vicinity  of  Hagerstown,  Maryland.  Tribes  Hill 
Limestone.  Amsterdam,  Canajoharie,  etc.,  New  York. 

Collection. — U.  S.  National  Museum. 

Genus  SOLENOPORA  Dybowski 

SOLENOPORA  COMPACTA    (Billings) 

Plate  XLI,  Figs.  1-3 

Stromatopora  compacta  Billings,  1865,  Pal.  Foss.,  vol.  i,  Geol.  Surv.  Canada, 

pp.  55,  212. 
Tetradium  peachii  Nicholson  and  Etheridge,  1877,  Ann.  and  Mag.  Nat.  Hist., 

4th  ser.,  vol.  xx,  p.  166,  text  figs.  d-g. 
Solenopora  spongioides  Dybowski,  1877,  Die  Chaetetiden  der  ostbaltischen 

Silur.  Formation,  p.  124,  pi.  ii,  figs,  lla-b. 
Tetradium  peachii  var.  canadense  Foord,  1883,  Cont.  Micro-Pal.,  Geol.  Surv. 

Canada,  p.  24,  pi.  vi,  figs.  1-lf. 
Solenopora  compacta  trentonensis  Brown,  1894,  Geol.  Mag.  London,  dec.  4, 

vol.  i,  p.  146,  text  fig.  2. 
Solenopora  compacta  Winchell  and  Schuchert,  1895,  Geol.  Minnesota,  Pal., 

vol.  3,  pt.  i,  p.  80,  pi.  F,  figs.  21-23. 
Actinostroma  trentonensis  Weller,  1893,  Geol.  Surv.  New  Jersey,  Pal.,  vol.  3, 

p.  139,  pi.  vi,  fig.  8;  pi.  vii,  figs.  3,  4. 


MARYLAND  GEOLOGICAL  SURVEY  193 

Description. — This  species  forms  small,  sub-globular  masses,  from 
one  to  two  inches  in  diameter.  The  concentric  lamellae  are  thin  and 
closely  packed  together,  there  being  in  some  specimens  from  6  to  12  layers 
in  the  thickness  of  two  lines. 

The  internal  structure  is  described  by  Dr.  Nicholson  as  follows: 
"  Composed  of  radiating  capillary  tubes,  arranged  in  concentric  strata. 
The  tubes  vary  from  1/12  to  1/20  mm.  in  size,  and  are  in  direct  contact 
throughout,  no  interstitial  tissue  of  any  kind  being  developed.  The  tubes 
are  irregular  in  form,  with  thin  often  undulated  walls,  which  are  not 
pierced  by  any  apertures  or  pores,  but  are  often  crossed  by  more  or  fewer 
transverse  partitions  of  ( tabulae/  Very  commonly  the  tubes  exhibit 
more  or  fewer  inwardly  directed  partitions,  which  extend  to  a  greater  or 
less  distance  into  the  cavity  of  the  tube,  and  are  the  result  of  the  cleavage 
or  '  fission  '  of  the  tubes." 

An  intensive  study  of  this  wide-spread  and  long-ranged  fossil  will  in  all 
probability  reveal  the  fact  that  a  number  of  distinct  species  are  included 
under  the  name  Solenopora  compacta. 

Occurrence. — CHAMBERSBURG  LIMESTONE  (Caryocystites  bed).  Fort 
London  and  localities  south  to  Blue  Spring,  Franklin  County,  Pennsyl- 
vania. A  wide-spread  and  abundant  fossil  in  almost  all  of  the  divisions 
of  the  Middle  and  Upper  Ordovician  in  North  America. 

Collections. — Maryland  Geological  Survey,  TJ.  S.  National  Museum. 

SPONGIAE  ?  (CALCAREOUS  ALGAE  ?) 

Genus  NIDILITES  Salter 
NIDULITES  PYRIFORMIS  Bassler.  i 

Plate  XLVI,  Figs.  1-5 

Nidulites  sp.  Bassler,  1909,  Bull.  Virginia  Geol.  Surv.,  vol.  iia,  pi.  vii,  fig.  11. 
Nidulites  pyriformis  Bassler,  1915,  Bull.  U.  S.  Nat.  Mus.,  no.  xcii,  p.  855. 

Description. — The  body  of  this  interesting  organism,  which  is  such  an 
abundant  fossil  at  certain  horizons  in  the  Chambersburg  limestone  of 
the  Appalachian  Valley,  is  pyriform  and  pedunculate,  with  an  outer 


194  SYSTEMATIC  PALEONTOLOGY 

covering  of  hexagonal,  cuplike  plates  fused  or  articulated  by  their  edges. 
On  the  exterior  each  plate  is  deeply  concave  and  marked  off  at  the  surface 
by  a  sharp  wall.  The  plates  are  smallest  at  the  narrow  end  of  the  organ- 
ism, but  increase  in  size  in  the  more  swollen  part  where  an  average 
diameter  for  them  of  one  millimeter  is  the  rule.  The  interior  of  the 
organism  is  hollow  (pi.  XLVI,  fig.  5)  and  is  frequently  filled  with  crystal- 
line calcite  (pi.  XLVI,  fig.  3) .  Specimens  about  35  mm.  in  length  are  the 
rule,  but  some  individuals  attain  a  length  of  50  mm. 

Small  fragments  of  Nidulites,  especially  where  partly  imbedded  in  the 
rock,  much  resemble  a  massive  bryozoan  with  large  zooecia,  but  examina- 
tion with  a  lens  reveals  the  very  different  nature  of  the  hexagonal  plates 
or  cups. 

The  systematic  position  of  Nidulites  is  still  quite  uncertain.     These 

bodies  were  supposed  by  Salter  to  be  the  egg-ribbons  of  marine  gastropods. 

•Later  paleontologists  placed  them  among  the  Protozoa,  but  to-day  the 

prevalent  opinion  is  that  they  are  allied  to  Receptaculites,  Cerionites, 

Ischadites  and  related  genera,  and  are  either  sponges  or  calcareous  algae. 

Occurrence. — CHAMBERSBURG  LIMESTONE  (Xidulites  bed).  Pennsyl- 
vania, Maryland,  and  Virginia.  Wilson,  Pinesburg  Station,  and  other 
localities  in  Maryland  furnish  numerous  specimens  of  the  species,  em- 
bedded in  the  rather  massive  strata  of  the  Xidulites  bed. 

Collection. — Maryland  Geological  Survey,  U.  S.  National  Museum. 

Genus  REGEPTACULITES  Def ranee 
RECEPTACULITES  OCCIDENTALS  Salter 

Plate  XLV,  Fig.  7  . 

Receptaculites   occidentalis   Salter,   1859,   Canadian   Org.   Remains,   dec.   i, 

p.  45,  pi.  x,  figs.  1-7. 
Receptaculites  occidentalis  Billings,   1865,   Pal.   Foss.,   vol.   i,   Geol.   Surv. 

Canada,  p.  381,  text  figs.  354-356. 
Receptaculites   occidentalis   Weller,    1903,    Geol.    Surv.   New   Jersey,    Pal., 

vol.  iii,  p,  135,  pi.  vi,  figs.  2-4. 


Description^-  ^Sponge  forming  discoid  or  flattened,  saucer-like  ex- 
pansions ;  attaining  a  diameter  of  200  mm.,  and  having  a  thickness  vary- 
ing from  4  mm.  at  the  center  of  the  disk  to  12  mm.  at  the  margin.  The 


MARYLAND  GEOLOGICAL  SURVEY  195 

disk  itself  composed  of  vertical  rods  or  spicules,  with  their  extremities 
expanded  and  more  or  less  flattened  to  form  the  two  surfaces  of  the  disk. 
The  shafts  of  the  spicules  are  cylindrical,  about  1  mm.  or  slightly  more  in 
thickness,  and  separated  from  each  other  by  interspaces  about  equal  to 
their  own  thickness.  The  arrangement  of  the  terminations  of  the  spicules 
upon  the  surface  of  the  disk  is  in  curved,  radiating  lines,  crossing  after 
the  manner  of  the  engine-turned  ornamentation  of  a  watch.  The  ex- 
panded outer  extremities  of  the  spicules  are  rhomboidal  in  outline,  leaving 
narrow,  linear  interstices  on  each  side  between  adjoining  spicules.  A 
short  distance  above  the  flattened,  rhomboidal  extremity  there  are  four 
connecting  processes,  which  join  the  spicule  with  each  of  the  adjoining 
ones.  The  inner  extremities  of  the  spicules  are  also  expanded  and  joined 
together  to  form  the  inner  surface  of  the  disk." — Weller,  1903. 

Occurrence. — CHAMBERSBURG  LIMESTONE  (Echinospherites  bed). 
Southern  Pennsylvania  and  at  Pinesburg  Station,  Maryland.  Black 
River  group  of  Canada,  New  Jersey,  Kentucky,  and  Arctic  America, 

Collection. — U.  S.  National  Museum. 

PORIFERA 

CLASS  SPONGIAE 

Genus  RHABDARIA  Billings 
RHABDARIA  FRAGILIS   (Billings) 

Rhabdaria  fragilis  Billings,  1865,  Pal.  Foss.,  vol.  i,  Geol.  Surv.  Canada,  p.  357. 
Rhabdaria  fragilis  Rauff,  1894,  Paleontographica,  vol.  xl,  p.  245. 

Description. — •"  Small  cylindrical  stems,  with  a  rough  exterior,  and  a 
central  perforation  or  canal.  At  first  these  were  thought  to  be  silicified 
specimens  of  Stenopora  fibrosa,  but  when  others  were  procured  showing 
the  central  canal,  it  became  evident  that  they  could  not  be  thus  referred. 
They  have  the  form  of  crinoidal  columns,  but  are  not  jointed.  No 
structure  can  be  made  out  in  thin  slices  under  the  miWRWp^?' — Billings, 
1865. 


196  SYSTEMATIC  PALEONTOLOGY 

Specimens  of  a  ramose  bryozoan-like  fossil  with  a  central  canal  have 
been  found  at  several  localities  in  the  Beekmantown  of  the  Appalachian 
Valley  in  Maryland  and  Pennsylvania.  These  agree  in  all  respects  with 
the  species  described  above  by  Billings,  which  unfortunately  has  never 
been  figured.  In  order  to  establish  the  species  the  original  types  or  speci- 
mens from  the  type  locality  must  be  further  investigated  and  illustrated. 
Until  this  has  been  done  the  identification  of  the  species  in  the  Appa- 
lachian Valley  must  be  considered  as  provisional.  The  type  specimens 
are  from  the  Romaine  division  of  the  Canadian,  Mingan  Islands,  Quebec. 

Occurrence. — BEEKMANTOWN  LIMESTONE.  Lower  part  above  the  Stone- 
henge  horizon,  just  east  of  Hagerstown,  Maryland.  Also  at  the  same  zone 
in  the  Chambersburg  quadrangle  of  Pennsylvania. 

Collection. — U.  S.  National  Museum. 

Genus  CAMAROCLADIA  Ulrich  and  Everett 
CAMAROCLADIA  RUGOSA  Ulrich 

Plate  XLII,  Fig.  6 

Camarocladia  rugosa  Ulrich,  1897,  Geol.  Minnesota,  vol.  iii,  pt.  2,  p.  xcv, 
foot  note. 

Description. — The  fucoid-like  remains  upon  which  this  species  is  based 
appear  to  be  the  cast  of  a  branching  sponge,  although  the  specimens 
seldom  show  structure  and  appear  most  frequently  as  flattened,  stony 
branches  with  more  or  less  obscure  oblique  and  transverse  furrows.  These 
compressed  flexuous  branches  bifurcate  sometimes  close  together  and 
other  times  far  apart.  The  branches  vary  from  5  to  over  12  mm.  in 
width  and  are  sometimes  so  crowded  in  the  rock  as  to  form  a  regular 
network  or  matting.  In  the  best  preserved  examples,  the  surface  is 
covered  with  an  irregular  network  of  coarse,  nodulose  threads  often 
arranged  longitudinally  and  generally  on  one  side  of  the  branch  only. 
When  removed  from  the  rock  the  stems  are  found  to  be  composed  of  two 
fairly  well-defined  portions,  (1)  a  siphuncle-like,  subcylindrical  rod, 
with  annulations  and  constrictions  3  to  6  mm.  apart,  and  (2)  a  series 
of  oblique  septa-like  partitions,  generally  two  to  each  annulation,  clasp- 


197 


ing  the  annulated  rod  so  as  to  leave  about  one-third  of  its  circumference 
exposed  to  view.  Sometimes  the  rod  changes  suddenly  from  one  side 
of  the  branch  to  the  other. 

Occurrence. — CHAMBERSBURG LIMESTONE  (Tetradium cellulosum bed). 
Fort  Loudon,  Franklin  County,  Pennsylvania.  An  abundant  species  in 
the  Decorah  shales  division  of  the  Black  Eiver  in  Goodhue  County, 
Minnesota,  and  at  the  same  horizon  in  Mercer  County,  Kentucky. 

Collections. — Maryland  Geological  Survey,  U.  S.  National  Museum. 

Order  TETRACTINELLIDA 

Family  HINDIIDAE 

Genus  HINDIA  Duncan 
HINDIA  PARVA  Ulrich 

Plate  L,  Figs.  11-13 

Hindia  parva  Ulrich,  1889,  Amer.  Geol.,  vol.  iii,  p.  244. 

Hindia  parva  Winchell  and  Schuchert,  1895,  Geol.  Minnesota,  vol.  iii,  pt.  1, 

p.  79,  pi.  G,  figs.  7-9. 
Hindia  parva  Weller,  1903,  Geol.  Surv.  New  Jersey,  Pal.,  vol.  iii,  p.  135,  pi.  vi, 

fig.  1. 

Description. — This  small  sponge  forms  free,  rounded  masses  with  a 
smooth  surface.  Most  of  the  specimens  are  about  7  mm.  in  diameter, 
although  this  dimension  varies  between  5  and  10  mm.  The  internal 
structure  is  very  similar  to  the  common  Hindia  sphaeroidalis  Duncan 
of  the  Silurian  and  Early  Devonian,  but  the  radiating  canals  of  H.  parva 
are  somewhat  smaller,  being  not  over  0.27  mm.  in  diameter.  More 
refined  methods  of  study  of  these  sponges  will  no  doubt  reveal  other 
important  differences. 

Occurrence. — MARTINSBURG  SHALE  (Sinuites  bed).  Chambersburg, 
Pennsylvania,  and  Strasburg,  Virginia.  Black  Eiver  of  Minnesota  and 
Wisconsin,  Trenton  of  Kentucky,  Tennessee,  New  Jersey  and  other  states. 

Collections. — Maryland  Geological  Survey,  U.  S.  National  Museum. 


198  SYSTEMATIC  PALEONTOLOGY 

COELENTERATA 

CLASS  ANTHOZOA 

Subclass  TETRACORALLA 

Family  CYATHOPHYLLIDAE 

Genus  GOLUMNARIA  Goldfuss 
COLUMNAKIA   (?)   HALLI  Nicholson 

Plate  XLI,  Fig.  5 

Columnaria  alveolata  Hall,   1847,   Pal.   New  York,   vol.    i,   p.   47,   pi.   xii, 

figs,  la-lc.  (not  Goldfuss). 
Columnaria  (?)  halli  Nicholson,  1879,  Tab.  Corals  Pal.  Period,  p.  198,  text 

figs.  28,  2;  p.  200,  text  fig.  29;  pi.  x,  figs.  3,  3a. 
Columnaria  (?)  halli  Winchell  and  Schuchert,  1895,  Geol.  Minnesota,  Pal., 

vol.  iii,  pt.  1,  p.  85,  pi,  G,  figs.  14-16. 

Description. — "  Corallum  forming  large  massive  colonies  which  vary 
from  a  few  inches  to  several  feet  in  diameter,  and  which  are  composed  of 
various  sized  polygonal  corallites,  in  close  contact  with  one  another 
throughout  their  entire  length.  The  walls  of  the  corallites  are  not 
excessively  thickened,  and  they  are  so  completely  amalgamated  in  con- 
tiguous tubes  that  even  under  the  microscope  the  original  lines  of 
demarcation  between  the  tubes  can  be  made  out  with  difficulty  or  not  at 
all.  The  large  tubes  are  usually  from  two  to  three  lines  in  diameter, 
though  occasionally  considerably  more  than  this,  and  the  smaller 
corallites  are  of  all  sizes.  Septa  marginal,  in  the  form  of  obtuse  longi- 
tudinal ridges  which  vary  in  number  from  20  to  40,  do  not  extend  to 
any  distance  into  the  visceral  chambers,  and  are  not  divisible  into  an 
alternating  longer  or  short  series.  Tabulae  strong,  horizontal  and  com- 
plete, about  half  a  line  apart  or  sometimes  closer.  Mural  pores  not 
recognized  with  certainty." — Winchell  &  Schuchert,  1895. 

Occurrence. — CHAMBERSBURG  LIMESTONE  ( Caryocystites  bed).  From 
Fort  Loudon  south  to  Blue  Spring,  Franklin  County,  Pennsylvania. 
Generally  an  abundant  fossil  in  the  Mohawkian  rocks  of  Canada  and  the 
United  States. 

Collections. — Maryland  Geological  Survey,  U.  S.  National  Museum. 


MARYLAND  GEOLOGICAL  SURVEY  199 

Family  ZAPHRENTIDAE 

Genus  STREPTELAS  .  A  Hall 

STREPTELASMA  PROFUNDUM  (Conrad) 

Plate  XLII,  Figs.  1,  2 

Cyathophyllum  profundum  Conrad,  1843,  Proc.  Acad.  Nat.  Sci.,  Philadelphia, 

p.  335. 
Streptelasma  profunda  Hall,  1847,  Pal.   New  York,  vol.   i,  p.   49,  pi.  xii, 

figs.  4a-d. 
Streptelasma  profundum  Winchell  and  Schuchert,  1895,  Geol.  Minnesota, 

Pal.,  vol.  iii,  pt.  i,  p.  88,  pi.  G,  figs.  17-19. 

Description. — "  Obliquely  turbinate,  often  slightly  curved  near  the 
base/ expanding  above  more  or  less  abruptly;  cell  profoundly  deep,  ex- 
tending nearly  to  the  base  of  the  coral ;  margin  of  the  cup  reflexed ;  sur- 
face scarcely  marked  by  transverse  rugae;  lamellae  from  36  to  60,  strong, 
nearly  equal  to  the  margin,  but  distinctly  alternating  in  length  within; 
no  transverse  dissepiments  or  celluliferous  structure." — Hall,  1847. 

This  well-marked  form  can  readily  be  separated  from  other  species  of 
the  genus  by  its  deep,  visceral  cavity,  by  its  sharply  denned  lateral  fos- 
sulae  and  great  development  of  the  primary  septum,  and  by  its  septa 
which  are  never  twisted  in  approaching  the  center. 

Occurrence. — CHAUBEKSBURG  LIMESTONE  (Tetradium  cellulosum  bed). 
Fort  Loudon,  Franklin  County,  Pennsylvania.  A  characteristic  and 
abundant  Black  Eiver  fossil  of  the  United  States  and  Canada. 

Collections. — Maryland  Geological  Survey,  IT.  S.  National  Museum. 

Suborder  TABULATA 
Family  CHAETETIDAE 

Genus  TETRADIUM  Dana 
TETRADIUM  ?  SIMPLEX  n.  sp. 

Plate  XXXIII,  Figs.  13-15 

Description. — The  discovery  of  a  coral  in  the  Beekmantown  limestone 
is  of  especial  interest  since  hitherto  no  typical  representative  of  the  corals 
has  been  recorded  from  strata  of  this  age.  The  species  here  noted  occurs 


200  SYSTEMATIC  PALEONTOLOGY 

abundantly  in  the  lower  Beekmantown  just  above  the  top  of  the  Stone- 
henge  member,  where  it  appears  in  lamellose  masses  on  the  weathered 
rock  surfaces.  Unfortunately  all  trace  of  the  structure  is  lost  in  the 
solid  rock  and  the  generic  determination  cannot  therefore  be  confirmed 
by  thin  sections.  The  corallites  are  polygonal,  with  rather  thick  walls 
which  sometimes  show  a  distinct  line  of  separation.  Three  corallites 
occur  on  an  average  in  2  mm.  No  septa  are  seen,  but  their  apparent 
absence  may  be  due  to  the  poor  preservation  of  the  specimens. '  The 
vertical  sections  exposed  by  weathering  show  no  tabulae. 

If  this  species  should  prove  to  be  an  early  representative  of  Tetradium 
it  will  be  readily  distinguished  from  the  other  species  of  that  genus  by  its 
small  corallites. 

Occurrence. — BEEKMANTOWN  LIMESTONE.  Just  above  the  Stonehenge 
member.  The  best  specimens  were  found  in  the  old  brick  yard  on  the 
eastern  edge  of  Hagerstown. 

Collections. — Maryland  Geological  Survey,  U.  S.  National  Museum. 

TETRADIUM  SYRINGOPOKOIDES  Ulrich 
Plate  XXXVIII,  Figs.  13-15 

Tetradium  sp.  Bassler,  1909,  Va.  Geol.  Surv.,  Bull.,  vol.  iia,  pi.  iv,  fig.  2. 
Tetradium  syringoporoides  Ulrich,  1910,  in  Stose,  Folio  U.  S.  Geol.  Surv., 
170,  p.  58. 

Description-. — This  species,  which  is  very  characteristic  of  the  Stones 
River  group,  has  been  known  for  a  number  of  years  by  the  students  of 
Appalachian  geology  as  the  "  single-tubed  Tetradium."  Certain  beds  of 
the  Stones  River  limestone  are  so  charged  with  these  tubes  that  they  give 
the  rock  a  coarse,  spongy  appearance.  Upon  weathering  the  individual 
tubes  stand  out  in  relief  like  pieces  of  cord,  but  in  fractured  fragments 
of  limestone  the  tubes  are  equally  distinct,  although  here  appearing  as 
stringers  of  calcite.  Upon  close  examination  the  coral  nature  of  this 
organism  becomes  evident,  for  the  tubes  divide,  giving  rise  to  either  two 
or  four  individual  tubes  which,  after  adhering  together  for  a  short  dis- 
tance, separate  and  in  turn  subdivide  as  before.  No  tabulae  are  visible 


201 

nor  are  any  signs  of  septa  to  be  observed  until  just  before  a  tube  divides 
when  the  characteristic  four  septa  of  Tetradium  are  developed.  A  normal 
corallite  is  quadrangular  and  about  two-thirds  of  a  millimeter  across. 

Occurrence. — STONES  RIVER  LIMESTONE.  Abundant  especially  in  the 
upper  division,  in  the  Appalachian  Valley.  In  Maryland  exposures  along 
the  line  of  outcrop  from  Pinesburg  Station  north  through  Wilson  to  the 
state  line  exhibit  numerous  examples. 

Collections. — Maryland  Geological  Survey,  U.  S.  National  Museum. 

TETRADIUM  COLUMNARE  (Hall) 
Plate  XLI,  Fig.  4 

Chaetetes  columnaris  Hall,  1847,  Pal.  New  York,  vol.   i,  p.  68,  pi.  xxiii, 

figs.  4,  4a. 
Tetradium  columnare  Safford,   1856,  Amer.  Jour.   Sci.  and  Arts,  2d  ser., 

vol.  xxii,  p.  237. 

Description. — "  Coral  massive,  hemispherical  or  subglobose,  consisting 
of  a  series  of  parallel  or  diverging  polygonal  tubes;  tubes  four-  or  five- 
sided,  simple,  without  visible  transverse  dissepiments  or  connecting  pores ; 
interior  of  the  cells  apparently  rugose  or  denticulate. 

"  The  rugose  structure  within  the  cell  probably  indicates  the  existence 
of  diaphragms  which  have  disappeared.  The  fossil,  in  its  general  form 
and  structure,  has  the  appearance  of  a  Favosites,  from  which  a  cursory 
examination  would  not  induce  us  to  separate  it.  A  closer  examination 
proves  that  the  tubes  are  usually  four-sided,  and  that  there  are  no  con- 
necting pores  in  the  walls  of  the  cells.  These  characters  had  decided  me 
to  separate  it  from  the  genus  Favosites,  before  knowing  fully  the  char- 
acters on  which  the  genus  Chaetetes  is  founded.  It  appears  referable 
to  the  latter  genus  from  its  general  similarity  to  some  of  the  species,  the 
character  of  quadrangular  cells  probably  being  unimportant  and  not 
constant.  The  apparent  absence  of  diaphragms,  or  transverse  dissepi- 
ments, is  perhaps  due  to  their  subsequent  destruction,  or  solution  and 
removal."— Hall,  1847. 

Occurrence. — CHAMBERSBDRG  LIMESTONE  ( Caryocystites  bed).  Fort 
London,  Pennsylvania. 


202  SYSTEMATIC  PALEONTOLOGY 

Not  uncommon  in  the  Trenton  rocks  of  New  York,  Kentucky,  and 
Tennessee.  Similar  forms  occur  in  the  Black  River  and  Stones  River 
formations  of  the  United  States  and  Canada. 

Collections. — Maryland  Geological  Survey,  IT.  S.  National  Museum. 

TETRADIIJM  CELLULOSUM  (Hall) 
Plate  XLII,  Figs.  3-5 

Phytopsis  cellulosum  Hall,  1847,  Pal.  New  York,  vol.  i,  pp.  39,  315,  pi.  ix, 
figs.  la-d. 

Description. — The  principal  features  of  this  index  fossil  of  the  Low- 
ville  limestone  are  well  shown  in  Hall's  original  illustrations  reproduced 
in  the  present  volume.  As  is  well  known,  the  main  specific  character  of  the 
fossil  is  the  occurrence  of  the  corallites  in  small  bunches  which,  in  the 
course  of  growth,  form  elongated,  subcylindrical  or  compressed  stems. 
These  stems  sometimes  anastomose,  forming  a  network.  In  transverse 
sections  the  generic  character  of  the  coral,  the  quadrangular  corallites 
with  four  regularly  placed  septa,  is  well  brought  out.  This  most  char- 
acteristic coral  of  the  Lowville  limestone  has  a  wide  distribution  in  New 
York  and  Canada  and  the  Appalachian  and  Ohio  valleys. 

Occurrence. — CHAMBERSBURG  LIMESTONE  (Tetradium  cellulosum 
bed).  Fort  Loudon  and  the  railroad  cut  two  miles  southwest  of  Marion,. 
Franklin  County,  Pennsylvania. 

Collections. — Maryland  Geological  Survey,  IT.  S.  National  Museum. 

CLASS  GRAPTOLITOIDEA 

Order  GRAPTOLOIDEA 

Family    DIPLOGRAPT1DAE 

Genus    GLIMACOGRAt  TUS    Hall 
CLIMACOGRAPTUS  PUTILLUS  (Hall) 

Plate  LII,  Figs.  5-7 

Oraptolithus  putillus   Hall,   1865,  Geol.    Surv.   Canada,   Org.   Rem.,   dec.   2, 

pp.  27,  44,  pi.  A,  figs.  10-12a. 
Climacograptus  putillus  Ruedemann,   1908,   Mem.   New   York   State  Mus., 

vol.  xi,  pt.  2,  pp.  415-419,  pi.  xxviii,  figs.  14,  15,  text  figs.  368-374,  376, 

377. 


MARYLAND  GEOLOGICAL  SURVEY  203 

Description. — "  Rhabdosome  very  small  (9  mm.  mostly  less)  and 
slender  (1-1.3  mm.  wide),  elliptic  in  section,  widening  gradually,  possess- 
ing a  gently  wavy  median  furrow  on  each  lateral  face.  Sicula  small 
(1.3  mm.)  and  very  slender,  provided  with  a  short  apertural  spine;  its 
slender  virgella  protruding  from  the  rhabdosome.  Thecae  tubular,  little 
inclined  to  the  axis  of  the  rhabdosome  in  the  proximal  half  and  sub- 
parallel  to  it  in  the  distal  free  half;  closely  arranged  (12-14  in  the  space 
of  10  mm.  or  32  in  1  inch)  ;  apertures  straight,  at  right  angles  to  longer 
axes  of  thecae.  Nemacaulus  thin." — Euedemann,  1908. 

A  common  species  of  the  Ohio  and  Mississippi  valleys,  New  York, 
Canada,  etc.,  ranging  from  t*he  Trenton  to  the  Richmond. 

Occurrence. — MARTINSBURG  SHALE  (Corynoides  bed).  Chambers- 
burg,  Pennsylvania,  and  Williamsport,  Maryland. 

Collections. — Maryland  Geological  Survey,  U.  S.  National  Museum. 

CLIMACOGRAPTUS  SPINIFER  (Ruedemann) 
Plate  LIT,  Figs.  3,  4 

Climacograptus  typicalis  mut.  spinifer  Ruedemann,  1908,  New  York  State 
Mus.  Mem.,  vol.  xi,  pt.  2,  pp.  411,  412,  pi.  xxviii,  figs.  8,  9,  text  fig.  236. 

Climacograptus  spiniferus  Ruedemann,  1912,  New  York  State  Mus.,  Bull. 
162,  p.  84. 

Description. — This  species  is  distinguished  from  the  well-known  Cli- 
macograptus typicalis  Hall,  which  it  most  closely  resembles,  in  the 
presence  of  two  straight,  thin  spaces  and  in  the  closer  arrangement  of  the 
thecae,  the  majority  of  the  specimens  having  14  thecae  in  10  mm.  In  the 
presence  of  the  two  spines  this  species  resembles  Climacograptus  bicornis 
Hall,  but  in  the  latter  species  these  spines  grew  from  the  first  two  thecae 
and  are  not  prolongations  of  the  sicular  spines  as  in  C.  spinifer. 

Occurrence.— MARTINSBURG  SHALE  (Corynoides  bed).  Chambers- 
burg,  Pennsylvania,  and  Williamsport,  Maryland.  Trenton  shale  of 
eastern  New  York. 

Collections. — Maryland  Geological  Survey,  TJ.  S.  National  Museum. 


204  SYSTEMATIC  PALEONTOLOGY 

CLIMACOGRAPTUS  BICORNIS  (Hall) 
Plate  LIU,  Fig.  1 

Graptolithus  bicornis  Hall,  1847,  Pal.  New  York,  vol.  i,  p.  268,  pi.  Ixxiii, 

figs.  2a-s. 
Climacograptus  bicornis  Elles  and  Wood,  1906,  Mon.  British  Grapt,  pt.  5, 

pp.  193,  194,  fig.  125,  pi.  26,  figs.  8a-f. 
Climacograptus  bicornis  Ruedemann,   1908,  Mem.  New  York   State  Mus., 

vol.  xi,  pt.  2,  pp.  433-437,  pi.  xxviii,  figs.  24-26,  figs.  404,  405. 

Description. — "  Synrhabdosome  not  observed.  Rhabdosome  linear  in 
the  middle  and  antisicular  portions;  attaining  great  length  (10  cm.  and 
more) ;  gradually  widening  from  the  sicular  extremity  to  a  width  of 
2. 6  +  mm.,  attained  in  about  30  mm.  and  maintained  close  to  the  anti- 
sicular extremity.  The  former  extremity  is  always  armed  with  two 
diverging  lateral  spines,  which  grow  from  the  first  two  thecae,  and  the 
virgella  which  greatly  varies  in  length.  The  sicula  is  1  mm.  long,  its 
greater  portion  embedded.  The  thecae  number  12  in  the  sicular  region 
and  seven  in  the  mature  part  and  overlap  about  one-third  their  length; 
their  proximal  walls  are  curved,  the  free  distal  wall  straight  and  parallel 
to  the  axis  of  the  rhabdosome.  The  apertural  margins  are  horizontal, 
the  apertural  excavations  wide  (one-third  length  of  theca)  and  attaining 
in  depth  one-fourth  the  width  of  the  rhabdosome  in  mature  part,  and 
one-third  in  the  earlier  part.  Nemacaulus  not  observed." — Ruedemann, 
1908. 

The  typical  form  of  this  wide-spread  species  has  been  recognized  in 
North  America  only  in  the  Chazyan,  but  varieties  or  very  closely  related 
species  occur  in  younger  formations  of  the  Ordovician.  In  southern 
Pennsylvania  and  Washington  County,  Maryland,  the  upper  beds  (Eden) 
of  the  Martinsburg  shale  furnish  a  species  of  Climacograptus  exhibiting 
the  diverging  points  at  the  base  characteristic  of  C.  bicornis. 

Occurrence. — MARTINSBURG  SHALE  (Eden  division).  Washington 
County,  Maryland. 

Collections. — Maryland  Geological  Survey,  TJ.  S.  National  Museum. 


MARYLAND  GEOLOGICAL  SURVEY  205 

Genus  DIPLOGRAPTUS  McCoy 

DIPLOGRAPTUS  VESPERTINUS  (Euedemann) 

Plate  LIII,  Figs.  2-4 

Diplograptus  pristis   (parte)   Hall,  1847,  Pal.  New  York,  vol.  i,  pi.  Ixxii, 

figs.  1,  la,  Ib,  Ik,  11. 
Diplograptus  foliaceus  mut.  vespertinus  Ruedemann,  1908,  Mem.  New  York 

State  Mus.,  vol.  xi,  pt.  2,  pp.  352-354,  pi.  xxv,  figs.  4,  5,  18,  text  figs. 

296-298. 

Description. — •"  Synrhabdosome  not  observed.  Ehabdosomes  as  a  rule 
short  (15  mm.,  greatest  length  observed  42  mm.),  widening  gradually 
from  an  initial  width  of  1  mm.  to  a  maximum  width  of  2.5  which  is 
attained  in  a  distance  of  15  mm.  from  the  sicular  extremity  and  then 
maintained.  Sicula  not  observed.  Sicular  extremity  furnished  with  a 
short  blunt  virgella  (about  .4  mm.  long)  and  two  equally  short  straight 
lateral  spines.  Thecae  numbering  11  to  13  in  10  mm.  (30-32  in  1  inch), 
inclined  at  an  angle  of  30° -40°,  overlapping  a  little  more  than  one-third, 
the  outer  margin  distinctly  convex,  the  proximal  part  frequently  slightly 
concave.  The  aperture  horizontal,  concave,  the  interthecal  excavation 
about  one-fourth  the  width.  Nemacaulus  very  thin  and  inconspicuous 
within  the  rhabdosome  and  not  seen  protruding  beyond  the  antisicular 
end/' — Ruedemann,  1908. 

The  types  are  from  the  Normanskill  (Chazyan)  shales  of  New  York 
and  the  species  has  been  identified  also  from  the  Trenton  shales  of  the 
same  state. 

Occurrence. — MARTINSBURG  SHALE  (Eden  division).  Jordans  Knob, 
one  and  one-half  miles  northeast  of  Fort  Loudon,  Pennsylvania,  and  in  the 
same  horizon  on  the  west  slope  of  Eickard  Mountain,  Maryland. 

Collection. — U.  S.  National  Museum. 


206  SYSTEMATIC  PALEONTOLOGY 

POSITION  UNCERTAIN 

Genus  CORYNOIDES  Nicholson 

CORYNOIDES  CALICULAEIS   Nicholson 

Plate  LII,  Figs.  1,  2 

Graptolite  germs  Hall,  1859,  Pal.  New  York,  vol.  iii,  p.  508,  fig.  7. 
Corynoides  calicularis  Nicholson,  1867,  Geol.  Magazine,  vol.  iv,  p.  108,  pi.  vii, 

figs.  9-11. 
Corynoides  calicularis  Weller,  1903,  Geol.  Surv.  New  Jersey,  Pal.,  vol.  iii, 

pp.  52,  214,  pi.  xvi,  figs.  12,  13. 
Corynoides  calicularis  Ruedemann,  1908,  New  York  State  Museum,  Mem., 

vol.  xi,  pt.  2,  pp.  234-237,  pi.  xiii,  figs.  1,  6-8,  text  figs.  122-132. 

Description. — "  Khabclosome  short  (6-8  mm.)  and  relatively  broad 
(about  1  mm.),  of  uniform  width,  consisting  of  a  sicula  and  three  thecae. 
Sicula  small  (2  mm.),  conical,  without  apertural  processes,  in  mature 
specimens  slightly  recurving,  suspended  from  a  long  and  slender  nema. 
Thecae  slender  tubes  of  uniform  width,  all  originating  close  to  the  sicula, 
arranged  in  a  bundle  which  forms  an  angle  of  50°  with  the  sicula. 
Apertures  straight,  normal  to  the  axes  of  the  thecae,  all  adjoining  at  the 
distal  extremity  of  the  rhabdosome,  each  provided  with  a  pair  of  usually 
curved  strong  spines,  which  often  appear  to  be  raised  upon  a  tongue- 
like  process.  Nema  thin  and  filiform/' — Euedemann,  1908. 

This  curious  little  graptolite  is  so  small  and  usually  so  poorly  preserved 
in  the  shales  that  its  presence  is  often  not  detected  without  careful  search. 
Weathered  shale  fragments  in  which  the  color  of  the  fossil  has  been 
changed  to  reddish  brown  or  even  white,  show  specimens  to  the  best 
advantage. 

Occurrence. — MARTINSBURG  SHALE  (Corynoides  bed).  Chambers- 
burg,  Pennsylvania,  Williamsport,  Maryland,  and  in  other  outcrops  to 
the  south.  Chazyan  (Normanskill)  shales,  New  York,  and  south  in  the 
Appalachian  Valley  to  Tennessee. 

Collection. — U.  S.  National  Museum. 


MARYLAND  GEOLOGICAL  SURVEY  207 

ECHINODERMATA      . 

CLASS  CYSTOIDEA 

Family  ECHINOSPHAERITIDAE 
Genus  ECHINOSPHAERI1  ES  Wahlenberg 

ECHINOSPHAERITES   AURANTIUM   AMERICANUM   n.    VRP. 

Plate  XLV,  Figs.  15-20 

Compare  Echinus  aurantium  Gyllenhal,  1772,  Kongl.  Vet.  Akad.  Handl., 
vol.  xxxiii,  p.  245,  pi.  viii,  figs.  4,  5;  pi.  9,  figs.  6-9. 

Description. — One  of  the  most  interesting  paleontological  discoveries 
in  the  Ordovician  limestone  of  the  Appalachian  Valley  of  Pennsylvania 
and  Maryland  was  that  of  numerous  large  globular  cystids  belonging  to 
the  genus  Echinospherites,  which  had  heretofore  not  been  recognized  in 
America.  One  division  of  the  Chambersburg  limestone  is  so  crowded 
with  these  cystids  that  the  name  Echinospherites  bed  has  been  applied 
to  it.  At  first  sight  these  cystids  appear  as  so  many  boulders  in  the  rock, 
and  indeed  in  the  past  the  strata  containing  them  have  doubtless  been 
considered  as  conglomerates.  Unweathered  specimens  show  no  definite 
structure  to  these  organisms  other  than  that  they  appear  to  be  globular 
masses  with  a  thick,  smooth  outer  covering.  When  weathered,  however, 
they  are  seen  to  be  composed  of  irregularly  arranged  plates  with  the 
numerous  canals  forming  the  pore  rhombs  especially  visible. 

The  various  species  of  Echinospherites  seem  to  have  been  distinguished 
by  European  paleontologists  mainly  by  their  differences  in  shape.  Com- 
paring the  figures  on  pi.  XLV  with  typical  E.  aurantium  from  the  Middle 
Ordovician  of  Esthonia,  Eussia,  it  will  be  noted  that  the  American  form 
is  larger  and  more  ovate.  For  this  reason  it  has  been  thought  best  to 
distinguish  it  as  a  variety  pending  a  thorough  study  of  the  group  by  some 
specialist.  The  common  name  of  "  crystal  apple  "  applied  to  species  of 
Echinospherites  in  Europe  is  very  appropriate,  first  because  of  their  shape 
and  second  because  the  interior  of  the  cystid  is  often  a  mass  of  calcite 
crystals.  American  specimens  are  often  found  with  a  crystalline  interior. 
14 


208  SYSTEMATIC  PALEONTOLOGY 

This  large  globular  cystid,  as  noted  above,  is  so  abundant  in  a  lower 
division  of  the  Chambersburg  limestone  that  it  has  received  the  name  of 
the  Echinospherites  bed.  The  reappearance  of  the  species  in  the  Chris- 
tiania  bed  was  noted  only  in  southern  Pennsylvania  where  a  few  speci- 
mens were  found  at  the  higher  horizon. 

Occurrence.  —  CHAMBERSBURG  LIMESTONE  (Echinospherites  bed). 
Appalachian  Valley  of  Pennsylvania,  Maryland,  West  Virginia,  and 
Virginia.  In  Maryland  specimens  have  been  found  at  Pinesburg  Station 
and  northward  along  the  line  of  outcrop  through  Wilson  to  the  state 
line.  The  same  form  reappears,  although  rarely,  in  the  Christiahia  bed 
of  the  Chambersburg  limestone  in  southern  Pennsylvania. 

Collections. — Maryland  Geological  Survey,  U.  S.  National  Museum. 

Genus  CARYOCYSTITES  Von  Buch 

CAEYOCYSTITES  sp. 
Plate  XLI,  Fig.  7 

Description. — The  strata  of  the  Chambersburg  limestone  underlying 
the  Lowville  division  contain  plates  of  a  species  of  the  cystid  genus 
Caryocystites  so  abundantly  that  the  name  Caryocystites  bed  has  been 
applied  to  them.  The  calyx  of  this  cystid  has  not  yet  been  found,  but  the 
plates  are  easily  recognized  by  the  elevated,  prominent  pore  rhombs  on 
their  external  surface.  When  weathered  the  plates  also  show  the  pores 
or  canals  connecting  with  the  pore  rhombs  and  passing  vertically  through 
the  plate. 

Occurrence. — CHAMBERSBUEG  LIMESTONE  (Caryocystites  bed).  Fort 
Loudon  and  south  to  Blue  Spring,  Franklin  County,  Pennsylvania. 

Collections. — Maryland  Geological  Survey,  U.  S.  National  Museum. 


MARYLAND  GEOLOGICAL  SURVEY  209 

CLASS  CRINOIDEA 

Order  GAMER  ATA  '     ' 

Family  RETEOCRINIDAE 
Genus  RETEOCRINUS  Billings 

KETEOCRINUS  ?  sp. 
Plate  XXXVII,  Fig.  5 

Description. — Small  plates  showing  six  or  seven  rays  are  not  uncommon 
on  the  surface  of  the  thin-bedded  Frederick  limestone.  These  are  of 
echinoderm  nature,  but  whether  cystid  or  crinoid  cannot  be  determined. 
They  appear  most  like  the  minute  pieces  forming  the  pliant  integument 
of  the  interbrachial  areas  in  such  crinoidal  genera  as  Reteocrinus. 

Occurrence. — FREDERICK  LIMESTONE.  In  the  vicinity  of  Frederick, 
Maryland.  .  • 

Collections. — Maryland  Geological  Survey,  U.  S.  National  Museum. 


Order  INADUNATA 

Family  CYATHOCRINIDAE 

Genus  CARABOGRINUS  Billings 

CARABOCRINUS  sp. 

Plate  XLI,  Fig.  10 

Description. — Associated  with  the  small  plates  of  the  cystid  Caryo- 
cystites  in  the  lowest  bed  of  the  Chambersburg  limestone  are  larger, 
strongly  marked  plates  of  a  crinoid.  These  bear  the  characteristic  mark- 
ings of  the  genus  Carabocrinus,  and  as  such  plates  are  known  only  from 
this  division  of  the  Chambersburg  limestone  an  illustration  of  one  has 
been  given  on  pi.  XLI  as  a  characteristic,  although  unnamed  fossil. 

Occurrence. — CHAMBERSBURG  LIMESTONE  (Caryocystites  bed).  Fort 
Loudon  south  to  Blue  Spring,  Franklin  County,  Pennsylvania. 

Collections. — Maryland  Geological  Survey,  U.  S.  National  Museum. 


210  SYSTEMATIC  PALEONTOLOGY 

Family    HETEROCRINIDAE 

Genus  HETEROGRINUS  Hall 

HETEEOCKINUS  HETEEODACTYLUS  Hall 

Plate  LIII,  Figs.  6,  7 

Heterocrinus   heterodactylus   Hall,    1847,   Pal.   New  York,   vol.   i,    p.   279, 

pi.  Ixxvi,  figs.  la-o. 
Heterocrinus  heterodactylus  Meek,  1873,  Geol.  Surv.  Ohio,  Pal.,  vol.  i,  p.  12, 

pi.  i,  figs.  la-b. 

Description. — "  Body  short,  rounded,  subcylindrical,  tapering  above 
and  below;  pelvis  composed  of  five  small  pentagonal  plates,  which  are 
succeeded  by  the  same  number  of  larger  costal  plates,  and  these  again  by 
five  scapulars ;  arms  irregularly  subdivided ;  column  pentagonal,  composed 
of  thick  joints,  which  are  nodulose  at  the  angles;  joints  alternating  in  size 
as  they  approach  the  pelvis. 

"  This  is  a  peculiar  species,  remarkable  for  the  small  size  of  the  body 
when  compared  with  the  column.  The  irregularity  of  the  arrangement 
of  the  plates  in  the  arms  and  fingers  is  likewise  a  striking  characteristic 
of  the  species,  which  is  constant  in  two  specimens  from  different  localities. 
In  one  of  the  arms,  the  scapular  plate  supports  a  regular  series  of  six  or 
more  plates  of  similar  form  without  division.  The  arms  at  the  right  and 
left  of  this  one  are  again  unlike  each  other.  The  one  on  the  left  has 
three  regular  and  gradually  diminishing  joints  above  the  scapular,  and 
of  the  same  form;  the  last  one  supports  the  cuneiform  joint,  which  again 
supports  a  double  row  of  joints  (or  a  pair  of  fingers).  The  arm  on  the 
right  of  the  first  mentioned  consists  of  a  pair  of  quadrangular  joints, 
each  of  which  supports  a  cuneiform  joint.  In  the  remaining  two  arms, 
no  plates  have  been  traced  beyond  the  scapulars,  and  consequently  the 
entire  form  of  the  species  cannot  be  determined.  Sufficient  is  visible, 
however,  to  show  the  irregular  character  of  the  arms,  from  which  its  name 
is  given."— Hall,  1847. 

Occurrence. — MARTINSBURG  SHALE  (Eden  division).  Pennsylvania 
and  Maryland.  A  splendid  mold  of  a  well-preserved,  entire  calyx  with  a 
considerable  column  attached  was  found  at  Jordans  Knob,  one  and  one- 


MARYLAND  GEOLOGICAL  SURVEY  211 

half  miles  northeast  of  Fort  London,  Pennsylvania.    Eden  shale  of  New 
York  and  the  Ohio  Valley. 

Collections. — Maryland  Geological  Survey,  U.  S.  National  Museum. 

Family  DENDROCRINIDAE 

Genus  MEROCRINUS  Walcott 

MEROCRINUS  sp. 

Plate  LIII,  Fig.  5 

Description-. — Only  stem  segments  of  this  crinoid  have  been  found  in 
the  upper  Martinsburg  shale,  but  the  genus  itself  is  so  characteristic  of 
the  Trenton  and  Eden  formations  that  it  was  thought  advisable  to  figure 
an  example  as  a  characteristic  fossil.  It  is  possible  that  the  segments 
here  illustrated  will  be  found  to  belong  to  the  only  known  Eden  species, 
M.  curtus  Ulrich,  from  the  Cincinnati  region. 

Occurrence. — MARTINSBURG  SHALE-  (Eden  division).    Jordans  Knob, 
one  and  one-half  miles  northeast  of  Fort  Loudon,  and  other  localities  in 
southern  Pennsylvania,  and  in  the  sandy  debris  on  the  west  slope  of 
Rickard  Mountain,  Washington  County,  Maryland. 
Collections. — U.  S.  National  Museum. 

CLASS  STELLEROIDEA 

Family    HUDSONASTERIDAE 

Genus  HUDSONASTER  Stiirtz 

HUDSONASTER  CLARKI  n.  Sp. 

Plate  LIII,  Fig.  8 

Description. — This  new  species  is  based  upon  two  specimens  preserved 
as  a  mold  in  sandy  shale  and  exhibiting  the  actinal  side.  The  species  is 
closely  related  to  H.  matutinus  (Hall)  from  the  Trenton,  and  is  indeed 
probably  descended  from  it,  but  the  Eden  form  differs  in  having  coarse 
tuberculations  on  the  axillary  plates  and  more  slender  and  more  regu- 
larly tapering  arms.  Further  differences  will  no  doubt  be  detected  when 
better  specimens  are  found,  but  the  above  seem  sufficient  to  discriminate 
the  species. 


212  SYSTEMATIC  PALEONTOLOGY 

The  specific  name  is  in  honor  of  the  late  Professor  William  Bullock 
Clark  in  appreciation  of  his  work  upon  fossil  echinoderm's. 

Occurrence. — MAKTIXSBUEG  SHALE  (Eden  division).  Jordans  Knob, 
one  and  one-half  miles  northeast  of  Fort  Loudon,  Pennsylvania. 

Collection. — U.  S.  National  Museum. 


MOLLUSCOIDEA 

CLASS  BRYOZOA 
order  CYCLOSTOMATA 

Family   DIASTOPORIDAE 
Genus   GORYNOTRYPA  Bassler 

COKYXOTRYPA  INFLATA    (Hall) 

Plate  XLVII,  Figs.  15-17 

Alecto  inflata  Hall,  1847,  Pal.  New  York,  vol.  i,  p.  77,  pi.  xxvi,  figs.  7a,  b. 
Stomatopora  inflata  Ulrich,   1893,  Geol.  Minnesota,  vol.  iii,  p.   117,  pi.  i, 

figs.  13-21. 
Uorynotrypa  inflata  Bassler,  1911,  Proc.  U.  S.  Nat.  Mus.,  vol.  xxxix,  p.  515, 

text  figs.  12-14. 

Description. — "  Zocecia  resembling  those  of  Hippothoa,  short  and  wide, 
pyriform,  the  proximal  end  contracted  and  springing  from  the  under  side 
of  the  anterior  end  of  the  cell  beneath ;  eight  or  nine  in  5  mm.  Apertures 
circular,  direct,  with  a  peristome,  about  0.09  mm.  in  diameter,  situated 
near  the  anterior  end.  Mural  perforations  minute  and  but  rarely 
preserved. 

"  In  the  Trenton  or  typical  form  of  this  species  the  zooecia,  as  a  rule, 
are  less  swollen  and  the  adnate  zoarium  divides  less  frequently  than  in 
the  better  known  Cincinnati  form.  In  the  latter,  therefore,  the  network 
is  closer,  and  occasionally  the  growth  is  so  luxuriant  that  the  rows  cross 
each  other  to  such  an  extent  that  but  little  space  is  left  between  the  cells. 
No  distinction,  however,  can  be  based  upon  these  characters  since,  when 
good  series  of  specimens  are  studied,  it  is  found  that  among  those  from 


MARYLAND  GEOLOGICAL  SURVEY  213 

Trenton  localities  some  have  more  than  commonly  swollen  and  crowded 
cells,  while  in  some  of  those  from  the  geologically  higher  localities  the 
growth  is  lax  and  the  zocecia  comparatively  narrow." — Ulrich,  1893. 

Occurrence. — CHAMBERSBURG  LIMESTONE  (Nidulites  bed).  Wilson, 
Maryland. 

Found  in  the  Black  River-Richmond  at  many  localities  in  the  United 
States  and  Canada. 

Collections. — Maryland  Geological  Survey,  U.  S.  National  Museum. 

CORYNOTRYPA  DELICATULA    (James) 

Plate  XLVII,  Figs.  12-14 

Hippothoa  delicatula  James,  1878,  The  Paleontologist,  No.  1,  p.  6. 
Stomatopora  tenuissima  Ulrich,  1893,  Geol.  Minnesota,  vol.  iii,  pt.  1,  p.  116, 

pi.  i,  figs.  16,  17. 
Stomatopora  proutana  Ulrich,  1893,  Geol.  Minnesota,  vol.  iii,  pt.  1,  p.  117, 

pi.  i,  figs.  8-12. 
Corynotrypa  delicatula  Bassler,   1911,  Proc.  U.   S.  Nat.  Mus.,  vol.  xxxix, 

p.  506,  text  figs.  3a,  4-7. 

Description. — This  neat  incrusting  fossil  is  extremely  abundant  in 
America  where  it  is  known  in  most  of  the  Ordovician  formations,  begin- 
ning with  the  Stones  River.  The  zocecia  vary  considerably  in  size  in  the 
different  forms  of  the  species,  but  maintain  the  same  relative  proportions. 

In  both  the  .large  and  small  forms  the  zoarium  is  incrusting  and  con- 
sists of  uniserially  arranged,  slender,  club-shaped  zocecia,  increasing 
gradually  in  size  from  the  narrow  proximal  end  to  the  rounded  anterior 
portion.  The  aperture  is  small,  sub  terminal,  with  a  slightly  elevated 
border,  and  about  one-third  the  diameter  of  the  anterior  third  of  the 
zocecia.  The  measurements  for  the  two  forms  are  as  follows:  Typical 
specimens  have  zocecia  0.04  mm.  in  diameter  at  the  proximal  end,  increas- 
ing to  0.12  to  0.15  mm.  at  the  widest  part  of  the  rounded  anterior  por- 
tion. The  zocecia  vary  from  0.6  to  0.8  mm.  in  length,  and  8  to  10  occur 
in  5  mm.  The  larger  form  varies  from  0.8  to  1.1  mm.  in  length  and 
from  0.2  to  0.3  mm.  in  diameter  at  the  anterior  portion.  The  stolon  is 
of  variable  length.  The  angle  of  divergence  in  both  large  and  small 
zocecia  is  about  15°. 


214  SYSTEMATIC  PALEONTOLOGY 

Occurrence. — CHAMBERSBURG  LIMESTONE  (Nidulites  bed).  Wilson, 
Maryland.  Stones  River-Bichmond  at  many  localities  in  the  United 
States  and  Canada. 

Collections. — Maryland  Geological  Survey,  U.  S.  National  Museum. 

Genus  BERENIGEA  Lamouroux 
BERENTCEA  VESICULOSA  Ulrich 

Plate  LIII,  Fig.  9 

Berenicea  vesiculosa  Ulrich,  1882,  Jour.  Cincinnati  Soc.  Nat.  Hist.,  vol.  v, 
p.  158,  pi.  vi,  fig.  5. 

Description. — •"  Zoarium  adnate,  very  delicate,  growing  usually  upon 
smooth  crinoid  columns.  Cells  showing  distinctly  upon  the  surface  as 
elliptical  convex  spaces,  with  the  circular  aperture  situated  upon  the 
forward  slope  of  the  same.  The  cells  are  closely  arranged  in  rather 
irregularly  alternating  series;  measured  along  the  length  of  the  cells, 
about  eight  may  be  counted  in  the  space  of  one  inch;  and  across  their 
width  11  or  12  occupy  the  same  space." — Ulrich,  1882. 

Occurrence. — MARTINSBURG  SHALE  (Eden  division).  Jordans  Knob, 
one  and  one-half  miles  northeast  of  Fort  London,  Pennsylvania.  Eden 
shale  of  the  Ohio  Valley. 

Collections. — Maryland  Geological  Survey,  U.  S.  National  Museum. 

.     '        order  TREPOSTOMATA 

Family  MONTICULIPORIDAE 

Genus  ORBIGNYELLA  Ulrich  and  Bassler 

ORBIGNYELLA  WETHERBYI  (Ulrich) 

Plate  X.LII,  Figs.  7,  8 

Monticulipora  wetherbyi  Ulrich,  1882,  Jour.  Cincinnati  Soc.  Nat.  Hist.,  vol.  v, 

p.  239,  pi.  10,  figs.  4-4b. 
Monticulipora  wether'byi  Ulrich,  1893,  Geol.  Minnesota,  vol.  iii,  p.  218;  pi.  xv, 

figs.  7,  8. 

Description. — Zoarium  attached,  forming  thin  crusts  or  small  de- 
pressed conical  masses  with  slightly  monticulose,  or  smooth  surfaces. 
Zocecia  polygonal,  with  very  thin  walls,  those  of  the  ordinary  size  with  a 


MARYLAND  GEOLOGICAL  SURVEY  215 

diameter  of  0.25  mm.  Clusters  of  larger  zooecia  form  the  monticules,  or 
are  scattered  over  the  surface  of  the  smooth  zooecia  at  intervals  of  about 
2.5  mm.,  measuring  from  center  to  center.  These  zocecia  measure  from 
0.30  to  0.38  mm.  in  diameter.  At  the  center  of  the  monticules  a  few 
mesopores,  or  more  probably  young  zooecia,  are  present.  Acanthopores 
rather  large  and  numerous. 

In  longitudinal  sections  the  zocecial  tubes  exhibit  thin  walls  with  the 
characteristic  granulose  structure.  The  diaphragms  are  curved  and  occur 
at  intervals  of  a  tube-diameter  or  more  in  the  lower  half  of  the  tubes  and 
about  one-third  that  distance  apart  near  the  surface.  In  tangential  sec- 
tions the  zocecial  walls  are  angular  and  thin  with  a  strong  acanthopore  at 
most  of  the  angles.  The  method  of  growth,  small,  angular,  thin-walled 
zocecia,  large  acanthopores,  granulose  wall  structure  and  the  presence  of 
curved  diaphragms  are  the  important  features  of  this  characteristic  and 
wide-spread  Lowville  fossil. 

Occurrence. — CHAMBERSBTJRG  LIMESTONE  (Tetradium  cellulosum 
bed).  Several  localities  south  of  Chambersburg  in  Franklin  County, 
Pennsylvania.  Lowville  limestone  of  the  Ohio  Valley,  etc. 

Collections. — Maryland  Geological  Survey,  U.  S.  National  Museum. 

Genus  PRASOPORA    Nicholson  and  Etheridge,  Jr 
PRASOPORA  INSULARIS  Ulrich 

Plate  XLIV,  Figs.  15-17 

Prasopora  insularis  Ulrich,  1893,  Geol.  Minnesota,  vol.  iii,  p.  251,  pi.  16, 
figs.  18-23. 

Description. — "  Zoarium  small,  discoid,  piano-  or  concavo-convex,  com- 
monly from  15-20  mm.  in  diameter  and  5  or  6  mm.  in  height.  In  a  very 
large  example  these  dimensions  are  respectively  28  and  12  mm.,  while  in 
the  smallest  seen  they  are  1.5  and  0.5  mm.  Under  surface  with  a  central 
scar,  and  beyond  it  delicate  radiating  lines,  fine  concentric  striae,  and,  at 
intervals  indicating  stages  of  growth,  stronger  wrinkles.  Very  often  the 
zoaria  are  evidently  made  up  of  distinct  superimposed  layers,  but  these 
are  not  usually  distinguishable  internally.  Upper  or  convex  surface  with- 
out monticules,  but  exhibiting,  at  intervals  of  about  4  mm.,  distinct 


216  SYSTEMATIC  PALEONTOLOGY 

clusters  of  large  zooecia.  Generally,  at  the  center  of  each  of  these  clusters, 
the  mesopores  which  are  small  and  in  nearly  all  cases  just  about  numerous 
enough  to  isolate  the  zooecia,  are  gathered  into  groups  of  varying  size. 
Zocecial  apertures  circular,  those  in  the  clusters  attaining  a  diameter  of 
0.4  mm.,  while  those  of  the  smaller  size  in  the  inter-macular  spaces 
average  about  0.22  mm.,  with  11  or  12  in  3  mm. 

"Internal  Characters:  The  first  peculiarity  to  be  noticed  in  tan- 
gential sections  is  the  relatively  great  abundance  of  the  mesopores.  In 
most  specimens  they  form  a  complete  ring  around  the  zocecia,  and  it  is 
chiefly  the  large  cells  in  the  clusters  that  are  occasionally  in  contact  at 
limited  points.  The  zocecial  walls  are  thin.  The  cystiphragms  are  more 
numerous  and  extend  to  a  less  distance  from  the  walls  than  in  any  other 
American  species.  The  opening  left  by  them  is  of  various  shapes,  gen- 
erally subangular,  and  often  removed  from  the  walls.  True  acanthopores 
have  not  been  detected. 

«  "  In  vertical  sections  the  abundance  of  the  mesopores,  the  narrowness 
of  the  cystiphragms,  and  the  unusual  crowding  of  the  tabulation  in  both 
sets  of  tubes,  are  the  distinctive  features.  In  the  mesopores  the  average 
number  of  diaphragms  in  1  mm.  is  over  25,  while  the  cystiphrams  may 
number  as  high  as  20  in  1  mm.,  though  the  average  is  not  likely  to  be 
over  15  in  that  space." — Ulrich,  1893. 

Occurrence. — CHAMBERSBURG  LIMESTONE  (Echinospherites  bed). 
Pinesburg  Station,  Maryland.  This  species  has  hitherto  been  known 
only  from  the  lower  Trenton  (Prosser  limestone)  of  Minnesota. 

Collections. — Maryland  Geological  Survey,  U.  S.  National  Museum. 

PRASOPORA  CONTIGUA  Ulrich 
Plate  XLVII,  Figs.  7,  8 

Prasopora  contigua  Ulrich,  1886,  Fourteenth  Ann.  Kept.  Geol.  Nat.  Hist. 

Surv.  Minnesota,  p.  87. 
Prasopora  contigua  Ulrich,  1893,  Geol.  Minnesota,  vol.  iii,  p.  249,  pi.  xvi, 

figs.  24-26. 

Description. — "  Zoarium  hemispheric,  base  flat  or  slightly  concave, 
usually  less  than  30  mm.  in  diameter.  Zocecia  with  very  thin  walls  and 


MARYLAND  GEOLOGICAL  SURVEY  21? 

polygonal  apertures,  10  or  11  of  the  average  size  in  3  mm.  Clusters  of 
zocecia,  some  of  them  attaining  a  diameter  of  0.37  mm.,  occur  at  intervals 
of  less  than  4  mm.  Mesopores  comparatively  few,  often  difficult  to  detect 
at  the  surface. 

"  Internal  Structure :  Tangential  sections  show  that  the  zocecial  walls 
are  polygonal  and  very  thin,  with  neighboring  cells  in  contact,  except  at 
many  of  the  angles  of  junction,  these  being  occupied  by  one  or  two  small 
mesopores.  The  latter  often  form  very  inconspicuous  clusters  at  the 
center  of  the  groups  of  large  zooacia,  but  in  the  intermediate  spaces  not 
over  half  of  the  angles  of  junction  between  the  ordinary  zocecia  are 
occupied  by  mesopores.  A  few  very  small  acanthopores  are  developed. 
The  opening  left  by  the  cystiphragms  is  generally  of  ovate  form  and  more 
often  eccentric  than  central  in  its  position  within  the  tube  cavity. 

"  Vertical  sections  are  peculiar  chiefly  because  they  exhibit  a  marked 
decrease  in  the  number  of  mesopores  when  compared  with  other  species 
of  the  genus." — Ulrich,  1893. 

Occurrence. — CHAM:BERSBURG  LIMESTONE  (Nidulites  bed).  Pennsyl- 
vania, Maryland,  and  Virginia.  The  cliffs  along  Conococheague  Creek 
at  Wilson,  Maryland,  exhibit  specimens  of  this  bryozoan.  A  not  uncom- 
mon fossil  of  the  Decorah  shale  division  of  the  Black  Eiver  group  of 
Minnesota. 

Collections. — Maryland  Geological  Survey,  U.  S.  National  Museum. 

Family  CONSTELLARIIDAE    . 

Genus  DIANULITES  Eichwald 
DlANULITES  PETROPOLITANUS  Dybowski 

Plate  XLIV,  Figs.  6,  7 

Dianulites  petropolitanus  Dybowski,  1877,  Die  Chaetetiden  der  Ostbaltischen 

Silurform.,  p.  24,  pi.  1,  figs.  4,  5. 
Diamilites  petropolitana  Bassler,  1911,  Bull.  U.  S.  Nat.  Mus.  No.  77,  pp.  232, 

237,  pi.  ii,  figs.  4-6a;  pi.  x,  figs.  7-11;  text  figs.  129-132. 
Monotrypa   (Chaetetes  ?)   cumulata  Ulrich,  1893,  Geol.  Minnesota,  vol.  iii, 

pt.  1,  p.  307,  pi.  xxvii,  figs.  26,  27. 

Description. — Zoarium  massive,  usually  hemispheric  with  a  slightly 
concave,  epithecated  base,  and  about  2.5  cm.  wide,  but  ranging  from  this 


218  SYSTEMATIC  PALEONTOLOGY 

to  large  expansions  10  or  more  centimeters  across.  Some  specimens  are 
of  irregular  shape,  but  almost  always  show  their  origin  from  the  usual 
hemispheric  forms.  Celluliferous  side  usually  smooth,  but  sometimes 
divided  into  polygonal,  usually  hexagonal,  areas  bounded  by  crestlike 
elevations  formed  of  mesopores.  At  the  center  of  these  areas  is  a  similarly 
elevated  cluster  of  mesopores  forming  the  macula.  Zooecia  thin-walled, 
polygonal,  averaging  four  in  2  mm.  Mesopores  few,  restricted  usually  to 
the  macula  and  to  the  edges  of  the  polygonal  areas  noted  above.  Acan- 
thopores  absent.  Diaphragms  placed  at  irregular  intervals  in  the  zooecial 
tubes,  but  usually  at  distances  varying  between  one  and  two  tube  diam- 
eters. In  the  mesopores  three  diaphragms  occur  in  a  distance  of  their  own 
diameter.  Walls  exhibiting  the  minute  granules  seen  in  the  typical 
species  of  Diamdites. 

Occurrence. — CHAMBERSBURG  LIMESTONE  (Echinospherites  bed). 
Pinesburg  Station,  Maryland.  Middle  Ordovician  of  Esthonia,  Russia, 
and  Goodhue  County,  Minnesota  (Prosser  limestone). 

Collections. — Maryland  Geological  Survey,  U.  S.  National  Museum. 

Family  TREMATOPORIDAE 

Genus  HEMIPHRAGMA  Ulrich 

HEMIPHRAGMA  IRRASUM  (Ulrich) 
Plate  XLIV,  Figs.  1-5 

Batostoma  irrasa  Ulrich,  1886,  Fourteenth  Ann.  Kept.  Geol.  Nat.  Hist.  Surv. 

Minnesota,  p.  94. 
Hemiphragma  irrasum  Ulrich,  1893,  Geol.  Minnesota,  vol.  iii,  p.  299,  pi.  xxiv, 

figs.  5-19. 
Hemiphragma  irrasum  Bassler,  1911,  Bull.  U.  S.  Nat.  Mus.,  No.  77,  pp.  284 

286,  text  figs.  172,  173. 

Description. — "  Zoarium  consisting  of  small,  subcylindrical,  frequently 
and  rather  irregularly  dividing  branches,  commonly  5  or  6  mm.  in  diam- 
eter, but  varying  from  4  to  8  mm.,  the  latter  extreme  probably  only  when 
an  extra  layer  of  tubes  has  grown  over  the  original  branch.  Monticules 
wanting,  but  under  fully  matured  conditions  the  surface  is  abundantly 
spinulose.  Zooecia  with  subangular  apertures  and  thin  walls  when  young, 


MARYLAND  GEOLOGICAL  SURVEY  219 

and  with  smaller,  subcircular  or  oval  apertures  and  more  or  less  thick 
walls  in  fully  matured  examples ;  arrangement  of  apertures  rather  regular 
in  rows  about  small  solid  spots,  in  the  immediate  vicinity  of  which  the 
zoo2cia  may  be  of  larger  size  than  elsewhere;  seven  to  nine  in  3  mm. 
Interspaces  apparently  solid  and  generally  with  shallow  irregular  depres- 
sions in  most  specimens,  but  in  very  young  stages  a  variable  number  of 
irregular  mesopores  may  be  recognized.  Acanthopores  numerous,  two 
or  more  to  each  zocecium,  situated  in  the  angles  of  junction  and  inter- 
spaces, and  increasing  in  size  with  age.  They  are  large  and  a  conspicuous 
external  feature  of  well-preserved  mature  examples. 

"  Internal  Characters:  In  the  axial  region  of  vertical  sections  the  tubes 
have  thin  and  irregularly  fluctuating  walls,  and  few  or  no  diaphragms. 
The  latter  are  complete  here  and  the  proximal  end  of  the  tube  expands 
to  full  size  with  unusual  rapidity.  In  the  peripheral  region,  which  is 
narrow  and  abruptly  distinguished  from  the  axial,  the  walls  are  more  or 
less  thickened,  and  the  tubes  intersected  by  semi-diaphragms,  about  four 
in  0.5  mm.  I  have  satisfied  myself  that  all  the  transverse  partitions  in 
this  outer  part  of  the  zocecial  tubes  are  really  incomplete.  That  many 
may  appear  entire  in  sections  is  only  because  their  inner  edge  happens 
to  be  vertical  instead  of  horizontal.  Mesopores  are  difficult  to  make  out 
in  these  sections,  being  short  and  usually  filled,  in  part  at  least,  with 
solid  tissue.  In  the  axial  part  of  transverse  sections  the  tubes  are  un- 
usually irregular  and  their  walls  comparatively  thick." — Ulrich,  1893. 

Occurrence. — CHAMBERSBURG  LIMESTONE  (Echinospherites  bed).  Sev- 
eral localities  in  southern  Pennsylvania  and  at  Pinesburg  Station,  Mary- 
land. Black  River  and  Early  Trenton  of  the  Upper  Mississippi  Valley. 

Collections. — Maryland  Geological  Survey,  U.  S.  National  Museum. 

Genus  DIPLOTRYPA  Nicholson 

DlPLOTRYPA    ?  APPALACHIA  n.  Sp. 

Plate  XLVII,  Figs.  9-11 

Description. — Zoarium  a  small  hemisphere  or  subconical  mass  averag- 
ing 20  mm.  in  width  and  10  to  15  mm.  high.  The  under  surface  exhibits 


220  SYSTEMATIC  PALEONTOLOGY 

extremely  small  tubes  which  indicate  that  the  reference  of  the  fossil  to 
the  Bryozoa  may  be  incorrect.  The  upper  surface  shows  extremely  large 
openings  for  a  bryozoan,  averaging  1  mm.  in  diameter,  with  thin  walls. 
In  thin  sections  these  cells  are  seen  to  be  separated  by  small,  irregular 
mesopore-like  structures.  Vertical  sections  are  particularly  interesting 
because  here  the  rapid  increase  in  diameter  of  the  tubes  from  the  minute 
pores  of  the  base  to  the  wide  openings  of  the  outer  part  is  well  shown. 
The  walls  in  such  sections  are  seen  to  be  thin  and  slightly  undulating. 
No  diaphragms  are  developed  in  either  the  larger  or  smaller  tubes. 

It  is  possible  that  more  extended  study  of  this  organism  will  show  it  to 
be  a  coral  related  to  Lichenaria,  but  most  of  the  evidence  at  present  seems 
to  indicate  its  relationship  to  the  Bryozoa. 

Occurrence. — CHAMBEESBURG  LIMESTONE.  This  fossil  and  Nidulites 
pyriformis  are  the  two  most  abundant  and  characteristic  species  ot 
the  Nidulites  bed  of  the  Chambersburg  formation.  The  comparatively 
large  tubes  of  this  bryozoan  may  be  seen  in  weathered  cross-sections 
wherever  the  more  massive  layers  of  the  Nidulites  beds  are  exposed. 
Pinesburg  and  Wilson,  Maryland,  afford  numerous  specimens. 

Collections. — Maryland  Geological  Survey,  TJ.  S.  National  Museum. 

Genus  BATOSTOMA  Ulrich 
BATOSTOMA  JAMESI  Nicholson 

Plate  LIV,  Figs.  1,  2 

Chaetetes  jamesi  Nicholson,  1874,  Quart.  Jour.  Geol.  Soc.  London,  vol.  xxx, 

p.  506,  pi.  xxix,  figs.  10,  lOb. 
Chaetetes  jamesi  Nicholson,  1875,  Pal.  Ohio,  vol.  ii,  p.  200,  pi.  xxi,  figs. 

11,  lla. 
Monticulipora  (Heterotrypa)  jamesi  Nicholson,  1881,  Genus  Monticulipora, 

p.  147,  figs.  25,  26. 
Batostoma  jamesi  Cumings,  1908,  32d  Ann.  Rep.  Dep.  Geol.  Nat.  Res.  Indiana, 

p.  775,  pi.  vii,  figs.  8,  8a;  pi.  viii,  fig.  1;  pi.  xxvli,  figs.  6,  6a. 

Description. — Zoarium  of  small,  rounded,  solid  stems  marked  at  the 
surface  by  large  oval  zocecia,  rather  conspicuous  acanthopores  and  numer- 
ous mesopores.  In  tangential  sections  the  walls  in  the  mature  region 
consist  of  thick,  dark  rings  of  dense  tissue  usually  widely  separated  from 


MARYLAND  GEOLOGICAL  SURVEY  221 

each  other  by  angular,  irregularly  shaped  mesopores.  Embedded  in  these 
walls  numerous  acanthopores  may  be  noticed.  In  longitudinal  sections 
the  zooecia  are  provided  with  rather  infrequent  complete  diaphragms  and 
mesopores  with  partitions  which  are  four  or  five  times  as  numerous. 

Occurrence. — MARTINSBURG  SHALE  (Eden  division).  Abundant  and 
characteristic  in  the  Eden  shale  of  the  Ohio  Valley.  Impressions  of  a 
ramose  bryozoan  in  the  upper  part  (Eden)  of  the  Martinsburg  shale  at 
Jordans  Knob,  one  and  one -half  miles  northeast  from  Fort  Loudon, 
Pennsylvania,  and  Cowans  Gap,  five  miles  northeast  of  McConnellsburg, 
Pennsylvania,  have  the  external  features  of  this  species.  * 

Collections. — Maryland  Geological  Survey,  U.  S.  National  Museum. 

Family  BATOSTO1WELLIDAE 

Genus  BYTHOPORA  Miller  and   Dyer 

BYTHOPORA  ARCTIPORA  (Nicholson) 

Plate  LIII,  Figs.  11-13 

Ptilodictya  f  arctipora  Nicholson,   1875,  Ann.   Mag.   Nat.   Hist.,    4th   ser., 

vol.  xv,  p.  180,  pi.  xiv,  figs.  4-4b. 
Ptilodictya  ?  arctipora  Nicholson,  1875,  Pal.  Ohio,  vol.  ii,  p.  262,  pi.  xxv, 

figs.  9-9b. 
Bythopora  arctipora  Bassler,  1906,  Proc.  U.  S.  Nat.  Mus.,  vol.  xxx,  p.  90, 

pi.  ii,  figs.  1,  2. 

Description: — This  minute  species  is  characterized  by  its  long,  slender, 
cylindrical  branches,  a  millimeter  or  less  in  diameter,  made  up  of  zocecial 
tubes  which  open  at  the  surface  in  elongate,  often  attenuate,  orifices. 
The  internal  structure  is  that  of  the  genus  Bythopora,  that  is,  the  zorecial 
walls  are  fused  in  the  mature  region,  diaphragms  are  practically  absent, 
the  apertures  are  oblique  and  narrowed  above,  and  the  interspaces  are 
canaliculate.  Mesopores  are  present  but  small,  and.  on  account  of  the 
small  size  and  little  development  of  the  zocecia  in  this  species,  they  are 
inconspicuous. 

Occurrence. — MARTINSBURG  SHALE  (Eden  division).  An  abundant 
and  characteristic  Eden  fossil  of  the  Ohio  Valley.  Not  so  abundant  in 


222  SYSTEMATIC  PALEONTOLOGY 

the  upper  part  (Eden)  of  the  Martinsburg  shale  at  Jordans  Knob,  one 
and  one-half  miles  northeast  of  Fort  Loudon,  Pennsylvania,  and  west 
slope  of  Eickard  Mountain,  Washington  County,  Maryland. 

Collections. — Maryland  Geological  Survey,  IT.  S.  National  Museum. 

Family    HALLOPORIDAE 
Genus  HALLOPORA  Bassler 

HALLOPOKA  ONEALLI  SIGILLAKIOIDES  (Nicholson) 

'  Plate  LIII,  Fig.  10 

Chaetetes  sigillarioides  Nicholson,  1875,  Pal.  Ohio,  vol.  ii,  p.  203,  pi.  xxii, 

figs.  9,  9a. 
Callopora  sigillarioides  Nickles,  1905,  Kentucky  Geol.  Surv.,  Bull,  v,  p.  50, 

pi.  ii,  figs.  10,  11. 
Callopora  onealli  sigillaroides  Bassler,  1906,  Proc.  U.  S.  Nat.  Mus.,  vol.  xxx, 

pi.  vi,  figs.  3,  4. 

Description. — Zoarium  ramose,  consisting  of  narrow,  dichotomously 
dividing  branches  from  2  to  4  mm.  in  diameter.  Surface  of  branches 
usually  smooth,  although  occasionally  the  clusters  of  larger  cells 
(maculae)  are  slightly  elevated.  Apertures  of  zocecia  oval,  about  six  in 
2  mm.  measuring  along  the  length  of  the  branch,  and  eight  in  the  same 
space  transversely  with  their  longer  diameter  in  the  direction  of  the 
branch.  Mesopores  numerous.  Diaphragms  few  in  the  axial  region  of 
the  tubes,  but  rather  numerous  in  the  mature  zone.  In  the  mesopores 
the  diaphragms  are  closely  spaced  throughout  their  length. 

Occurrence. — MARTINSBURG  SHALE  (Eden  division).  Very  abundant 
and  characteristic  of  the  Eden  shale  in  the  Ohio  Valley.  Upper  part 
(Eden)  of  Martinsburg  shale  at  Jordans  Knob,  one  and  one-half  miles 
northeast  of  Fort  Loudon ;  Cowan's  Gap,  five  miles  northeast  of  McCon- 
nellsburg,  and  Tuscarora  Mountain,  two  and  one-half  miles  southeast  of 
McConnellsburg,  Pennsylvania.  The  corresponding  horizon  in  Maryland 
on  Eickard  Mountain,  Washington  County,  also  furnishes  specimens.  In 
all  of  the  eastern  localities  the  species  occurs  as  molds  in  the  sandy 
matrix,  but  the  preservation  is  so  good  that  gutta  percha  squeezes  readily 
show  all  of  the  specific  characters  of  the  surface. 

Collections. — :Maryland  Geological  Survey,  U.  S.  National  Museum. 


MARYLAND  GEOLOGICAL  SURVEY  223 

order  CRY PTOSTOM ATA 

Family  PTILODICTYONIDAE 

Genus  ESCHAROPORA  Hall 
ESCHAROPORA   CONFLTJENS  Ulrich 

Plate  XL,  Figs.  11-14 

Escharopora  confluens  Ulrich,  1893,  Geol.  Minnesota,  vol.  iii,  p.  171,  pi.  xiil, 
figs.  1-11. 

Description. — "  Zoarium  branching,  the  smallest  seen  less  than  25  mm. 
high,  with  the  branches  averaging  about  2.5  mm.  in  width;  the  largest 
fragments  indicate  a  hight  of  from  80  to  120  mm.,  and  in  these  the  width 
of  the  branches  varies  from  4  to  8  mm.  The  two  surfaces  of  the  branches 
are  generally  obtusely  ridge-shaped,  and  in  the  largest  a  row  of  monti- 
cules, or  simply  clusters  of  large  cells,  occurs  on  the  summit  of  the  ridge. 
Edges  thin  and  sharp,  commonly  with  a  coarsely  striated  or  pitted  narrow 
border.  Through  all  stages,  though  less  distinct  in  the  oldest,  the 
zocecial  apertures  are  narrow  and  appear  to  be  drawn  out  at  the  ends  so 
as  to  connect  by  means  of  a  narrow  channel.  This  confluent  character 
of  the  zocecial  apertures  is  better  shown  and  more  regular  in  the  central 
rows,  where  they  are  also  narrower  and  on  the  whole  considerably  smaller 
than  toward  the  margins.  In  the  central  rows,  10  in  5  mm.  lengthwise ; 
18  or  19  in  5  mm.  diagonally,  and  five  and  one-half  in  1  mm.,  and  10  in 
2  mm.,  transversely ;  of  longitudinal  rows  there  are  19  or  20  in  2  mm. 

"  Tangential  sections  show  that  the  base  of  the  zorecia,  excepting  those 
in  the  marginal  rows,  is  bounded  by  very  thin,  straight,  longitudinal  wall,, 
and  equally  thin  transverse  partitions.  This  portion  of  the  zocecium 
therefore  may  be  described  as  a  parallelogram,  with  the  length  and 
breadth  respectively  as  four  is  to  one.  At  about  the  middle  of  the  hight 
of  the  primitive  cell  its  sides  have  spread  a  little  and  the  ends  contracted 
in  a  corresponding  degree.  Just  as  the  posterior  half  is  about  to  be 
roofed  over  two  projections  from  the  side  walls,  at  a  point  a  little  behind 
the  middle,  gradually  converge  until  they  meet  and  thereby  cut  off  and 
15 


224  SYSTEMATIC  PALEONTOLOGY 

enclose  the  elliptical  primitive  aperture.  In  the  succeeding  stages  the 
principal  change  is  a  reduction  in  the  size  of  the  apertures,  caused  by  an 
internal  deposit."— Ulrich,  1893. 

Occurrence. — CHAMBERSBURG  LIMESTONE  (Caryocystites  bed).  Blue 
Spring,  Franklin  County,  Pennsylvania.  The  type  specimens  of  this 
species  were  found  in  the  Decorah  shales  division  of  the  Black  Eiver  at 
Minneapolis,  Minnesota. 

Collections. — Maryland  Geological  Survey,  U.  S.  National  Museum. 

Genus  ARTHROPORA  Ulrich 

AETHEOPORA  BIFURCATA  Ulrich 

Plate  XLVIII,  Figs.  13-15 

Arthropora  bifurcata  Ulrich,  1893,  Geol.  Minnesota,  vol.  iii,  p.  178,  pi.  xiv, 
figs.  22-25. 

Description. — "  Segments  small,  thin,  with  sharp  edges  and  rather  wide 
nonporiferous  border,  the  lower  ones  bifurcating,  usually  only  once;  so 
far  as  observed  not  over  8  mm.  long,  and  from  1.2  to  1.8  mm.  wide;  the 
upper  joints  shorter,  their  length  occasionally  less  than  5  mm.,  bifurcat- 
ing or  with  a  single  lobe-like  projection  on  one  or  both  sides.  Young 
segments  with  comparatively  large,  ovate  zocecial  apertures,  not  very 
regularly  arranged  in  longitudinal  and  diagonally  intersecting  series, 
with  about  nine  in  3  mm.  lengthwise,  and  five  in  1  mm.  diagonally. 
Apertures  enclosed  in  distinct  granulose  rims,  connecting  longitudinally. 
Interspaces  depressed,  sometimes  with  a  few  indistinct  striae.  With  age 
the  zocecial  apertures  become  more  circular  and  smaller,  and  the  peri 
stomes  and  connecting  ridges  thicker." — Ulrich,  1893. 

Occurrence. — CHAMBERSBURG  LIMESTONE  (Christiania  bed).  Green- 
castle  and  other  localities  in  southern  Pennsylvania. 

Black  Eiver  and  early  Trenton  of  Minnesota,  Kentucky,  Tennessee, 
and  Canada. 

Collections. — Maryland  Geological  Survey,  U.  S.  National  Museum. 


MARYLAND  GEOLOGICAL  SURVEY  22p 

ARTHROPORA  CLEAVELANDI  (James) 
Plate  LIII,  Figs.  14,  15 

Ptilodictya  cleavelandi  James,  1881,  Paleontologist,  No.  5,  p.  38. 
Arthropora  cleavelandi  Bassler,  1906,  Proc.  U.  S.  Nat.  Mus.,  vol.  xxx,  p.  xiv, 
pi.  3,  figs.  13-16;  pi.  4,  fig.  6. 

Description. — Ptilodictya  cleavelandi  James,  as  shown  by  the  type,  is 
founded  upon  segments  of  a  rather  well-marked  species  of  Arthropora 
occurring  abundantly  throughout  the  various  subdivisions  of  the  Eden 
shale.  The  species  is  characterized  by  slender,  generally  nonbifurcating 
segments  (in  consequence  of  which  the  complete  zoarium  must  have  con- 
sisted of  comparatively  only  a  few  rigid  branches)  and  by  the  numerous 
and  small  lateral  branchlets  springing  out  at  nearly  right  angles  from  the 
main  stem.  The  segments  are  usually  found  separated,  specimens  retain- 
ing more  than  a  sequence  of  two  or  three  being  extremely  rare.  Ir 
length  they  vary  but  little  from  the  average  of  7  mm.  The  basal  seg- 
ment is  bifurcated  and  drawn  out  acuminately  below. 

The  zocecial  apertures  are  as  usual  in  this  genus,  elliptical,  surrounded 
by  a  delicate  peristome.  The  interspaces  have  one  or  more  thread-like 
ridges,  variously  disposed  and  with  a  row  of  minute  papillae. 

Occurrence. — MARTINSBURG  SHALE  (Eden  division).  Pennsylvania 
and  Maryland.  Jordans  Knob,  one  and  one-half  miles  northeast  of  Fort 
Loudon  and  Tuscarora  Mountain,  two  and  one-half  miles  southeast  of 
McConnellsburg,  in  Pennsylvania,  and  the  western  slopes  of  Fairview  and 
Rickard  Mountains,  Washington  County,  Maryland,  are  localities  where 
the  species  may  be  found. 

A  characteristic  and  abundant  species  of  the  Eden  shale  at  Cincinnati, 
Ohio,  and  vicinity. 

Collections. — Maryland  Geological  Survey,  IT.  S.  National  Museum. 


226  SYSTEMATIC  PALEONTOLOGY 

Family  PHYLLOPORINIDAE 

Genus  GHASMATOPORA    Eichwald 

CHASMATOPORA  EETICULATA  (Hall) 

Plate  XL,  Pigs.  4-6 

Intricaria  f  reticulata  Hall,  1847,  Pal.  New  York,  vol.  i,  p.  77,  pi.  xxvi, 

figs.  8a-c. 
Phylloporina  reticulata  Ulrich,  1890,  Geol.  Surv.  Illinois,  vol.  viii,  pp.  332, 

639,  pi.  liii,  figs.  2,  2a. 
Phylloporina  reticulata  Ulrich,  1893,  Geol.  Minnesota,  vol.  viii,  p.  210,  pi.  iv, 

figs.  8-15. 
Chasmatopora  reticulata  Bassler,  1911,  Bull.  U.  S.  Nat.  Mus.,  No.  77,  pp.  170, 

171,  text  fig.  86. 

Description. — "  Specimens  as  seen,  consisting  of  small,  flat  or  undulat- 
ing, reticulate  expansions,  being  in  each  case  evidently  fragments  of  a 
depressed,  funnel-shaped  zoarium,  probably  not  exceeding  5  cm.  in 
diameter.  Branches  rounded  in  section,  0.2  to  0.3  mm.  in  diameter, 
inosculating  at  unusually  frequent  and  regular  intervals.  Fenestrules 
somewhat  elongate,  about  as  wide  as  the  branches,  subrhomboidal  in 
shape  in  the  more  regularly  constructed  fragments;  their  number  in  a 
given  space  is  fairly  constant,  the  extremes  noticed  in  1  cm.  being  10 
and  12.  Reverse  of  branches  convex  finely  striated  lengthwise. 

"  Obverse  strongly  convex,  with  three  rather  irregular  rows  of  zooecia, 
their  apertures  subcircular,  with  a  distinct  peristome,  about  0.1  mm.  in 
diameter,  eight  or  nine  in  2  mm.  Acanthopores  abundant,  irregularly 
distributed,  rather  large,  especially  so  in  the  earliest  forms  of  the  species. 
Interspaces  slightly  concave,  occasionally  faintly  pitted  and  striated. 

"  In  tangential  sections  the  zooecia  are  rather  short,  with  a  row  on 
each  side  directed  obliquely  outward,  and  one  series  between  them.  The 
latter  are  wedge-shaped,  and  in  deep  sections  appear  as  a  more  or  less 
narrow  central  space.  Diaphragms,  one  in  each  tube,  have  been  observed." 
Ulrich,  1893. 

Occurrence. — CHAMBERSBURG  LIMESTONE  (Caryocystites  bed).  Fort 
Loudon  and  Blue  Spring,  Franklin  County,  Pennsylvania.  The  original 
types  are  from  the  Trenton  limestone  of  New  York,  but  the  species  has  a 
wide  distribution  in  both  the  Black  River  and  Trenton  rocks. 

Collections. — Maryland  Geological  Survey,  U.  S.  National  Museum. 


MARYLAND  GEOLOGICAL  SURVEY.  227 

CHASMATOPORA  SUBLAXA  (Ulrich) 
Plate  XL,  Figs.  7-10 

Phylloporina  sullaxa  Ulrich,  1890,  Journ.  Cincinnati  Soc.  Nat.  Hist,  vol.  xii, 

p.  179,  fig.  6. 
Phylloporina  sullaxa  Ulrich,  1893,  Geol.  Minnesota,  vol.  iii,  p.  209,  pi.  iv, 

figs.  1-7. 

Description. — "  Zoarium  an  undulating  flabellif  orm  expansion,  attain- 
ing a  diameter  of  5  cm.  or  more,  consisting  of  irregularly  inosculating 
slender  subcylindrical  branches,  varying  in  width  from  0.3  to  0.6  mm., 
but  averaging  about  0.45  mm.  Fenestrules  large,  subacutely  elliptical, 
varying  considerably  in  shape  and  size,  generally  two  or  three  time^ 
longer  than  wide ;  measuring  longitudinally,  the  average  number  in  1  cm 
is  between  five  and  six ;  transversely,  nine  or  ten  in  the  same  space.  These 
measurements  apply  to  the  Tennessee  specimens.  In  the  Minnesota  form 
of  this  species  the  fenestrules  are  smaller,  averaging  between  six  and 
seven  in  1  cm.  lengthwise. 

"  Reverse  of  the  Tennessee  specimens  strongly  rounded,  nearly  smooth, 
or  with  faint  longitudinal  striae.  In  very  young  examples  the  latter 
would  probably  be  more  distinct." — Ulrich,  1893. 

Occurrence. — CHAMBERSBURG  LIMESTONE  ( Caryocystites  bed).  Fort 
Loudon  and  Blue  Spring,  Franklin  County,  Pennsylvania. 

Specimens  from  the  Stones  Biver,  Black  Eiver,  and  Chazyan  rocks  have 
been  identified  with  the  types  of  this  species  which  were  found  in  the 
Upper  Stones  Eiver  limestone  of  Central  Tennessee. 

Collections. — Maryland  Geological  Survey,  U.  S.  National  Museum. 

Family  ARTHROSTYLIDAE 

Genus  HELOPORA   Hall 
HELOPORA  DIVARICATA  Ulrich 

Plate  XL,  Figs.  1-3 

Helopora  divaricata  Ulrich,  1886,  Fourteenth  Ann.  Kept.  Geol.  Surv.  Min- 
nesota, p.  59. 

Helopora  divaricata  Ulrich,  1893,  Geol.  Minnesota,  vol.  iii,  p.  191,  pi.  iii, 
figs.  1-3. 

Helopora  divaricata  Bassler,  1911,  Bull.  U.  S.  Nat.  Mus.,  No.  77,  pp.  149-150, 
text  fig.  72. 


228  SYSTEMATIC  PALEONTOLOGY 

Description. — "  Zoarium  jointed ;  segments  about  7.0  mm.  long,  obtuse 
at  both  extremities,  subcylindrical,  polygonal  in  cross-section,  the  number 
of  the  angles  and  corresponding  rows  of  zocecial  apertures  six,  seven  or 
eight.  Their  diameter  varies  with  age  and  according  to  the  number  of 
zorecia  contained  from  0.5  to  0.9  mm.  Zooacial  apertures  comparatively 
large,  oblique,  ovate,  seeming  to  widen  anteriorly,  arranged  in  troughs 
between  strong  longitudinal  ridges,  12  in  5  mm.  lengthwise  and  generally 
in  regular  transverse  rows.  Posterior  border  of  apertures  thick,  promi- 
nent, sloping  backward  into  the  aperture  next  below.  This  border  is 
continued  upon  the  sides  of  the  zocecial  aperture  as  two  diverging  ridges 
which  extend  on  each  side  to  the  summit  of  the  longitudinal  keels  where 
they  meet  with  similar  ridges  from  the  adjoining  rows.  These  divaricat- 
ing ridges  cause  the  strong  vertical  keels  to  appear  as  being  marked  by  a 
succession  of  narrow  A-shaped  furrows  and  ridges.  Occasionally,  and 
this  is  true  more  especially  of  the  young  and  slender  segments,  the 
rounded  posterior  slope  is  divided  by  a  central  furrow  into  two  small 
ridges."— Ulrich,  1893. 

Occurrence. — CHAMBERSBURG  LIMESTONE  (Caryocystites  bed).  Fort 
Loudon,  Franklin  County,  Pennsylvania.  This  species  has  heretofore 
been  recorded  from  the  Decorah  shales  of  the  Black  Eiver  group  of  Minne- 
sota and  the  Kuckers  shales  of  Esthonia,  Eussia. 

Collections. — Maryland  Geological  Survey,  U.  S.  National  Museum. 

HELOPORA  SPINIFORMIS  (Ulrich) 
Plate  XLIV,  Figs.  8-10 

Arthroclema  spiniformis  Ulrich,   1882,   Jour.   Cincinnati   Soc.   Nat.   Hist., 

vol.  v,  p.  161,  pi.  vi,  figs.  10,  lOa. 
Helopora  spiniformis  Ulrich,  1893,  Geol.  Minnesota,  vol.  iii,  pi.  iii,  figs.  4-6. 

Description. — •"  Zoarium  composed  of  numerous  segments,  which  are 
cylindrical,  poriferous  on  all  sides,  and  pointed  more  or  less  obtusely  at 
each  end;  their  length  varies  from  two-  to  four-tenths  of  an  inch,  their 
diameter  from  .015  inch  to  .04  inch.  Cell  apertures  oblique,  arranged 
between  slightly  elevated  longitudinal  lines,  and  in  transverse  rows 
around  the  stem.  On  account  of  their  obliquity,  well-preserved  examples 


MARYLAND  GEOLOGICAL  SURVEY  229 

have  the  lower  margin  of  the  aperture  prominently  elevated.  There  are 
from  8  to  16  longitudinal  series  of  cell-apertures  around  the  segments; 
seven  of  the  transverse  series  occupy  the  space  of  .1  inch.  Longitudinal 
sections  show  that  the  cells  radiate  from  a  central  axis,  that  their  walls 
are  thin  near  the  axis,  and  become  much  thickened  as  they  approach  the 
surface.  No  diaphragms.  In  transverse  sections  the  cells  radiate  from 
the  central  axis,  and  appear  as  so  many  wedges  arranged  around  a  central 
point."— Ulrieh,  1893. 

Occurrence. — CHAMBERSBURG  LIMESTONE  (Echinospherites  bed). 
Pinesburg  Station,  Maryland.  Lebanon  limestone  division  of  the  Stones 
Eiver  group  at  Lebanon  and  other  localities  in  Central  Tennessee. 

Collections. — Maryland  Geological  Survey,  U.  S.  National  Museum. 

Family    RHINIDICTYONIDAE 

Genus  RHINIDICTYA   Ulrieh 
RHINIDICTYA  NEGLECTA  Ulrieh 

Plate  XLIV,  Figs.  11-14 

Stictopora  paupera  (in  part)  Ulrieh,  1886,  Fourteenth  Ann.  Kept.  Geol.  Nat. 

Hist.  Surv.  Minnesota,  p.  69. 
Rhinidictya  neglecta  Ulrieh,  1893,  Geol.  Minnesota,  vol.  iii,  p.  130,  pi.  v, 

figs.  22-25. 

Description. — "  Zoarium  small,  branches  dividing  dichotomously  at 
intervals  of  from  4  to  7  mm.,  rather  convex,  the  margins  parallel,  not 
very  sharp,  and  with  non-cellulif erous  border  variable.  Width  of  tranches 
rather  constant  at  about  1.5  mm.  Zocecia  in  8  to  11  ranges,  the  usual 
number  nine,  with  rather  small,  elliptical,  oblique  apertures,  about  17  in 
5  mm.  lengthwise,  and  six  in  1  mm.  transversely.  In  most  cases  all  the 
apertures  are  directed  longitudinally  or  parallel  with  the  edges  of  the 
branches;  in  others,  however,  those  forming  the  marginal  row  on  each 
side  may  be  turned  slightly  outward.  Interspaces  comparatively  thick, 
less  ridge-shaped  than  usual,  often  slightly  zigzag,  with  the  range  of 
granules  well  developed. 

"  Internal  structure  chiefly  diagnostic  in  vertical  sections.  These  show 
that  the  primitive  or  prostrate  cell  is  comparatively  elongate,  and  that  at 


330  SYSTEMATIC  PALEONTOLOGY 

the  turn  into  the  '  vestibule '  the  wall  is  merely  sharply  curved  and  not 
angular,  as  in  R.  mutabilis."— Ulrich,  1893. 

Occurrence. — CHAMBERSBURG  LIMESTONE  (Echinospherites  bed). 
Southern  Pennsylvania  and  Pinesburg  Station,  Maryland.  Lower  Tren- 
ton of  Kentucky,  Tennessee,  and  Minnesota. 

Collections. — Maryland  Geological  Survey,  IT.  S.  National  Museum. 

,      .      .         BRACHIOPODA 

Order  ATREMATA 

Family  OBOLIDAE 

Genus  LINGULELLA  Saiter 

LlNGULELLA  Sp. 

Description. — No  fossils  have  been  found  in  the  Waynesboro  formation 
in  Maryland,  but  Stose  records  the  discovery  of  a  few  poorly  preserved 
shells  in  the  sandy  shales  at  the  top,  just  each  of  Waynesboro  in  Pennsyl- 
vania. These  were  identified  as  an  undetermined  species  of  Lingulella 
suggesting  Middle  Cambrian  age.  Better  preserved  material  is  necessary 
before  any  stratigraphic  use  can  be  made  of  this  species,  and  for  that 
reason  it  has  not  been  figured. 

Occurrence. — WAYNESBORO  FORMATION.  Just  east  of  Waynesboro, 
Pennsylvania. 

Collection. — U.  S.  National  Museum. 

Genus  LEPTOBOLUS  Hall 
LEPTOBOLUS  ?  OVALIS  n.  sp. 

Plate  XLIX,  Figs.  14-16 

Description. — This  interesting  little  brachiopod  is  associated  with  the 
quite  similar  Lingula  riciniformis  Hall  from  which  it  can  be  distin- 
guished externally  by  its  more  rounded  beak.  Internally  the  valves  of 
this  new  Leptobolus  show  the  two  or  three  diverging,  slightly  elevated 
septa  characteristic  of  the  genus,  but  these  are  so  faintly  developed  that 


MARYLAND  GEOLOGICAL  SURVEY  231 

the  species  cannot  be  considered  typical.  Paterula,  which  differs  from 
Leptobolus  in  having  the  inner  margins  of  the  valves  thickened,  must  also 
be  considered  in  determinating  its  final  generic  position. 

Compared  with  other  species  of  Leptobolus,  L.  ovalis  is  distinguished 
at  once  by  its  larger  size,  more  elongated,  oval  shape,  more  rounded  beak 
and  less  clearly  marked  interior. 

Occurrence. — MARTINSBURG  SHALE  (Sinuites  bed).  Many  localities  in 
the  Chambersburg  and  Mercersburg  quadrangles  of  Pennsylvania  and  in 
the  southern  extension  of  the  same  strata  into  Maryland.  The  figured 
specimens  are  from  the  locality  two  miles  northeast  of  Kauffman,  Penn- 
sylvania. 

Collections. — Maryland  Geological  Survey,  U.  S.  National  Museum. 

LEPTOBOLUS  INSIGNIS  Hall 
Plate  LIT,  Fig.  13 

Leptobolus  insignis  Hall,  1871,  Fossils  from  Hudson  River  Group,  p.  3,  pi.  iii, 
fig.  17  (Twenty-fourth  Kept.  New  York  State  Cab.  Nat.  Hist.,  p.  227, 
pi.  vii,  fig.  17). 

Leptobolus  insignis  Hall  and  Clarke,  1892,  Pal.  New  York,  vol.  viii,  pt.  i, 
p.  74,  pi.  iii,  figs.  1-6. 

Description. — Shell  semiphosphatic,  minute,  1.50-2.00  mm.  in  length, 
fragile,  orbicular,  with  a  scarcely  pointed  beak.  Valves  subcircular, 
regularly  convex  and  marked  with  concentric  lines  of  growth  on  the 
exterior  surface.  Ventral  valve  with  a  distinct  pedicle  groove  and  an 
elevated  subquadrate  muscular  area  on  its  interior.  The  dorsal  valve  is 
somewhat  thickened  on  the  cardinal  margin  and  bears  slightly  elevated, 
trifid  muscular  impressions.  The  internal  surface  with  radiating  striae 
separates  this  species  from  other  forms  of  the  genus. 

Occurrence. — MARTINSBURG  SHALE  (Corynoides  bed).  Chambers- 
burg,  Pennsylvania,  and  Williamsport,  Maryland.  Utica  shale  of  New 
York,  Canada,  and  the  Ohio  Valley. 

Collections. — Maryland  Geological  Survey,  TJ.  S.  National  Museum. 


238  SYSTEMATIC  PALEONTOLOGY 

Family  LINGULIDAE 

Genus  LINGULA    Bruguiere 

LlNGULA  RICINIFORMIS   Hall 

Plate  L,  Figs.  6-8 

Lingula  riciniformis  Hall,  1847,  Pal.  New  York,  vol.  i,  p.  95,  pi.  xxx,  fig.  2. 
Lingula    (Glossina)    riciniformis  Hall  and  Clarke,   1892,   Pal.  New  York, 

vol.  viii,  pt.  i,  pi.  i,  fig.  3. 
Lingula  riciniformis  Winchell  and  Schuchert,  1893,  Minnesota  Geol.  Surv. 

pt.  iii,  p.  343,  fig.  24;  pi.  xxix,  fig.  9. 
Lingula  riciniformis  Weller,  1903,  Geol.  Surv.  New  Jersey,  Pal.  3,  p.  144. 

pi.  ix,  fig.  8. 

Description. — Shell  oval  to  subelliptical  in  outline  with  the  two  valves 
equally  convex;  an  average  specimen  is  8  mm.  long  and  4  mm.  wide. 
Anterior  margin  regularly  rounded,  lateral  margins  slightly  convex,  sub- 
parallel;  postero-lateral  margins  rounded  and  apex  rather  blunt.  Sur 
face  nearly  smooth  or  marked  by  very  fine  concentric  lines  of  growth 
Fine  radiating  striae  are  sometimes  visible. 

As  pointed  out  by  Winchell  and  Schuchert  in  1893  this  shell  is  of 
particular  interest  in  showing  the  three  stages  of  development  very 
clearly.  The  first  shelled  condition  or  "  protegulum "  is  very  small ; 
second  comes  a  sharply  defined  circular  stage,  termed  the  Obolella  stage, 
distinguished  furthermore  by  its  lighter  color,  and  third  arises  the  stage 
in  which  the  shell  begins  to  assume  its  specific  form.  Through  the 
addition  of  shell  substance  posterior  to  the  protegulum  the  apex  at 
maturity  is  no  longer  marginal  as  in  the  Obolella  stage,  but  has  become 
submarginate. 

Occurrence. — MARTINSBURG  SHALE  (Sinutes  bed).  Chambersburg, 
Pennsylvania,  and  Strasburg,  Virginia.  Trenton  limestone  of  New  York, 
Canada,  Minnesota,  and  New  Jersey. 

Collections. — Maryland  Geological  Survey,  U.  S.  National  Museum. 

LINGULA  NICKLESI  n.  sp. 

Plate  LVII,  Figs.  1-U 

Description. — The  sandstones  of  Lower  Maysville  age  in  the  Appa- 
lachians contain  specimens  of  a  Lingula  which  upon  close  comparison 
prove  to  be  identical  with  a  species  from  the  upper  part  of  the  Fairview 


MARYLAND  GEOLOGICAL  SURVEY  233 

division  of  the  Maysville  at  Cincinnati,  Ohio,  and  vicinity.  This  species 
has  the  subquadrangular  outline  of  Lingula  elderi  Whitfield  from  the 
Black  Eiver  group  of  Minnesota  and  Wisconsin,  but  its  anterior  end  is 
more  drawn  out.  It  is  also  closely  related  to  L.  rectilateralis  Emmons 
from  the  Utica  shales  of  New  York,  but  lacks  the  fine  radiating  striae  of 
that  species,  is  more  elongate  and  less  quadrate. 

Occurrence. — MARTINSBURG  SHALE  (Orthorhynchula  bed  at  the  top-of 
the  Fairview  division).  Head  of  Eaver's  Eun,  three  and  one-half  miles 
southwest  of  Saxton,  Pennsylvania. 

The  figured  specimens  are  from  the  upper  part  of  the  Fairview  forma- 
tion at  Cincinnati,  Ohio. 

Collection. — U.  S.  National  Museum. 

.  order  NEOTREMATA      • 

Family  OBOLELLIDAE 

Genus  OBOLELLA  Billings 

OBOLELLA  MINOR  (Walcott) 

Plate  XXV,  Figs.  1-4 

Camarella  minor  Walcott,  1890,  Proc.  U.  S.  Nat.  Mus.  for  1889,  vol.  12, 

pp.  36-37. 
Camarella  ?  minor  Walcott,  1891,  Tenth  Ann.  Kept.  U.  S.  Geol.  Survey,  p.  614, 

pi.  Ixxii,  figs.  4,  4a-d. 
Camarella  minor  Hall  and  Clarke,  1894,  Nat.  Hist.  New  York,  Paleontology, 

vol.  8,  pt.  2,  p.  221. 
Obolella  minor  Clark  and  Mathews,  1906,  Maryland  Geol.  Survey,  vol.  6,  pt.  1, 

p.  252,  pi.  xvi,  figs.  13  and  14. 

Description. — "  General  form  ovate,  biconvex.  Surface  smooth  or 
marked  by  concentric  lines  and  varices  of  growth.  Ventral  valve  suba- 
cuminate,  moderately  convex,  with  the  most  elevated  portion  at  the  umbo, 
which  curves  toward  the  small  apex ;  the  posterior  or  umbonal  third  of  the 
valve  is  usually  more  or  less  tumid,  a  ridge  of  growth  separating  it  from 
the  anterior  portion  of  the  shell ;  area  nearly  on  the  plane  of  the  margins  of 
the  valve  and  divided  midway  by  narrow,  deep,  pedicle  furrow;  casts  of 
the  interior  show  that  the  area  formed  a  shelf  on  each  side  of  the  pedicle 
furrow.  Dorsal  valve  transversely  ovate;  a  narrow,  short  area  and  a 
slight  median  ridge  are  indicated  on  a  cast  of  the  interior. 


234  SYSTEMATIC  PALEONTOLOGY 

"  This  shell  is  small.  A  large  ventral  valve  measures,  length  7  mm. : 
width,  6  mm.;  a  dorsal  valve,  length  6  mm.;  width,  6.5  mm." — Walcott. 

Occurrence. — ANTIETAM  SANDSTONE.  Mouth  of  Little  Antietam 
Creek  near  Eakles  Mills,  one  mile  east-southeast  of  Smithsburg  and  other 
localities  in  Washington  County,  Maryland. 

Collections. — Maryland  Geological  Survey,  U.  S.  National  Museum. 

Family  DISCINIDAE 

Genus  ORBIGULOIDEA  D'Orbigny 

ORBICULOIDEA  LAMELLOSA  (Hall) 

Plate  XLVIII,  Fig.  12 

Orbicula  lamellosa  Hall,  1847,  Pal.  New  York,  vol.  i,  p.  99,  pi.  xxx,  fig.  10 

(not  Broderip,  1833). 
Orbiculoidea  lamellosa  Hall  and  Clarke,  1892,  Pal.  New  York,  vol.  viii,  pt.  1, 

pi.  4E,  fig.  12. 
Orbiculoidea  lamellosa  Weller,  1903,  Geol.  Surv.  New  Jersey,  Pal.,  vol.  iii, 

p.  147,  pi.  ix,  figs.  1,  2. 

Description. — "  Shell  depressed-conical,  nearly  circular  in  outline,  the 
apex  of  the  brachial  valve  situated  about  one-third  of  the  breadth  of  the 
shell  from  the  margin.  Surface  marked  by  rather  irregular,  elevated, 
more  or  less  lamellose,  concentric  lines,  the  grooves  between  the  lines 
being  rather  wider  than  the  ridges  themselves. 

"  The  dimensions  of  a  nearly  perfect  brachial  valve  are :  Length, 
9.5  mm. ;  width,  8.75  mm. ;  convexity,  2.5  mm." — Weller,  1903. 

Occurrence. — CHAMBERSBUEG  LIMESTONE  (Christiania  bed).  Penn- 
sylvania and  Virginia.  Trenton  limestone  of  Middleville,  etc.,  New  York, 
New  Jersey,  and  Ontario. 

Collection. — U.  S.  National  Museum. 

Family  ACROTRETIDAE 
Genus  CONOTRETA  Walcott 
CONOTRETA  RUSTI  Walcott 

Plate  L,  Figs.  1-5 

Conotreta  rusti  Walcott,  1890,  Proc.  U.  S.  Nat.  Mus.,  vol.  xii,  p.  365,  figs.  1-4. 
.  Conotreta  rusti  Hall  and  Clarke,  1892,  Pal.  New  York,  vol.  viii,  pt.  i,  p.  104, 
pi.  4K,  figs.  16-21. 


MARYLAND  GEOLOGICAL  SURVEY  235 

Description.— Shell  small,  calcareo-corneous,  circular  in  outline  and 
cone-shaped  in  form ;  2  to  3  mm.  in  height.  Pedicle  valve  conical  with  the 
height  greater  than  the  length.  Apex  usually  broken,  but  showing  evi- 
dence of  the  external  opening  of  the  sipho.  Extending  from  the  apex  to 
the  posterior  margin  is  a  shallow  furrow  increasing  in  width  downward. 
The  posterior  wall  of  the  shell  conforms  to  the  curvature  of  the  rest  of 
the  surface  in  small  specimens,  but  this  area  becomes  distinctly  flattened 
in  larger  examples,  as  in  Acrotreta.  Surface  covered  with  sharp  con- 
centric striae  curving  slightly  upward  as  they  cross  the  foraminal  groove. 

In  casts  of  the  interior  a  strong  apical  callosity  marking  the  probable 
position  of  the  foramen  is  produced  anteriorly  into  a  short,  sharp  ridge, 
on  either  side  of  which  lie  two  other  ridges,  with  evidence  of  a  third  on  the 
lateral  slopes. 

The  highly  conical  form  of  this  calcareo-corneous  shell  and  the  numer- 
ous radiating  ridges  on  the  ventral  interior  readily  distinguish  this 
interesting  brachiopod. 

Occurrence. — MARTINSBURG  SHALE  (Sinuites  bed).  Chambersburg, 
Pennsylvania,  and  Strasburg,  Virginia.  Trenton  limestone,  Trenton 
Falls,  Xew  York. 

Collection. — U.  S.  National  Museum. 

Family  TREMATIDAE 

Genus  SGHIZOGRANIA  Hall  and  Whitfield 

SCHIZOCRANIA  FILOSA  (Hall) 

Plate  LII,  Figs.  8,  9 

OrUcula  ?  filosa  Hall,  1847,  Pal.  New  York,  vol.  i,  p.  99,  pi.  xxx,  fig.  9. 
Schizocrania  fllosa  Hall  and  Whitfield,  1875,  Pal.  Ohio,  vol.  ii,  p.  73,  pi.  i, 

figs.  12-15. 
Schizocrania  filosa  Weller,  1903,  Geol.  Surv.  New  Jersey,  Pal.,  vol.  iii,  p.  146, 

pi.  ix,  figs.  3,  4. 

Description. — "  Shell  orbicular  or  subovate,  the  beak  of  the  free  or 
brachial  valve  projecting  slightly  beyond  the  limits  of  the  circle,  giving 
a  somewhat  greater  diameter  along  the  median  line  than  in  a  transverse 
direction.  Pedicle  or  attached  valve  discoid,  very  thin,  deeply  and  broadly 


236  SYSTEMATIC  PALEONTOLOGY 

notched  on  the  posterior  side;  the  notch  occupying  nearly  one-quarter 
of  the  circumference  of  the  valve  on  the  outer  margin  and  extending 
nearly  to  the  center  of  the  valve,  its  border  thickened,  especially  at  the 
base,  which  is  rounded,  with  the  center  marked  by  a  slightly  projecting 
point,  marked  by  strong,  irregular,  concentric  undulations  parallel  to  the 
margin,  but  interrupted  by  the  border  of  the  notch.  Brachial  or  free 
valve  moderately  convex,  most  prominent  near  the  center,  its  surface 
marked  by  fine,  even,  thread-like,  radiating  striae,  which  increase  both  by 
bifurcation  and  intercalation,  and  become  stronger  toward  the  border 
of  the  shell."-— Weller,  1903. 

This  interesting  brachiopod  ranges  in  age  from  the  Trenton  to  the 
Richmond,  the  best  localities,  however,  being  in  the  Trenton  of  New  York 
and  the  Maysville  of  the  Ohio  Valley.  In  the  Cumberland  Valley  the 
species  is  known  only  in  the  lower  part  (Corynoides  bed)  of  the  Martins- 
burg  shale. 

Occurrence. — MARTINSBURG  SHALE  (Corynoides  bed).  Williamsport, 
Maryland. 

Collections. — Maryland  Geological  Survey,  U.  S.  National  Museum. 

Family  CRANIIDAE 

Genus  PHOLIDOPS  Hall 

PHOLIDOPS  CINCINNATIENSIS  Hall 

Plate  LIV,  Figs.  23,  24 

Pholidops  cincinnatiensis  Hall,  1872,  24th  Kept.  New  York  State  Cab.  Nat. 

Hist,  pi.  vii,  fig.  10. 
Pholidops  cincinnatiensis  Meek,  1873,  Pal.  Ohio,  vol.  i,  p.  130,  pi.  v,  fig.  2. 

Description. — •"  Shell  small,  ovate  in  outline.  Larger  valve  about  one- 
fifth  longer  than  wide,  with  height  one-third  to  one-fourth  the  breadth. 
Apex  obtuse,  near  half  way  between  the  middle  and  the  larger  end. 
Anterior  end  narrowly  rounded,  posterior  end  somewhat  more  broadly 
rounded,  or  almost  sub-truncate.  Surface  ornamented  by  six  or  seven 
sub-imbricating  marks  of  growth.  Smaller  valve  unknown. 

"Length,  0.14  inch,  0.12  inch;  height  of  larger  valve,  0.04  inch/' — 
Meek,  1873. 


MARYLAND  GEOLOGICAL  SURVEY  237 

Occurrence. — MARTINSBURG  SHALE  (Eden  division).  Molds  and  casts 
showing  the  specific  characters  quite  plainly  are  found  at  Jordans  Knob 
one  and  one-half  miles  northeast  of  Fort  London,  Cowans  Gap,  five  miles 
northeast  McConnellsburg,  and  Tuscarora  Mountain  two  and  one-half 
miles  southeast  McConnellsburg,  Pennsylvania.  In  Maryland  the  same 
horizon  on  Eickard  Mountain,  Washington  County,  has  afforded 
specimens.  Not  uncommon  in  the  Eden  and  Maysville  strata  of  the 
Ohio  Valley. 

Collections. — Maryland  Geological  Survey,  U.  S.  National  Museum. 

Order  PROTREMATA 
Superfamily  ORTHACEA 
Family  BILLINGSELLIDAE 

Genus  EOORTHIS  Walcott 

EOORTHIS  DESMOPLEURA  (Meek) 

Plate  XXVII,  Figs.  1-5 

Orthis  desmopleura  Meek,  1872,  Hayden's  U.  S.  Geol.  Surv.  Wyoming,  p.  295. 
Orthis    (Plectorthis)    desmopleura  Walcott,   1905,   Proc.   U.   S.  Nat.   Mus., 

vol.  xxviii,  p.  261. 
Eoorthis  desmopleura  Walcott,  1912,  Mon.  U.  S.  Geol.  Surv.,  vol.  li,  p.  777, 

pi.  xcvi,  figs.  1,  la-r. 

Description. — "  This  shell  has  the  general  form  and  external  characters 
of  E.  wichitaensis  (Walcott).  It  differs  in  being  less  convex  and  in  the 
details  of  the  radiating  ribs.  Eoorthis  desmopleura  differs  from  E.  rem- 
nicha  (N.  H.  Winchell)  in  its  uniformly  smaller  size,  less  convexity,  and 
in  the  details  of  the  radiating  ribs.  The  ribs  have  a  wide  range  of  varia- 
tion, but  when  from  the  same  character  of  matrix  they  are  all  of  the  same 
type  and  the  shells  grade  from  one  to  the  other.  The  ventral  valves  of 
young  shells  2  to  3  mm.  long  are  highly  convex  and  usually  appear  to  be 
a  little  longer  than  wide ;  if  in  such  shells  the  surface  striae  are  in  sharply 
elevated  fasiculae,  the  result  is  to  all  appearances  a  rhynchonelloid 
shell. 


238  SYSTEMATIC  PALEONTOLOGY 

"  The  interior  of  the  ventral  valve  shows  a  narrow  area,  broad  delthy- 
rium,  spondylium  almost  free  from  the  bottom  of  the  valve,  and  a  median 
septum  that  may  have  supported  the  front  end  of  the  spondylium.  In 
young  and  strongly  convex  shells  the  spondylium  is  narrow  and  very 
strongly  defined.  The  narrow  area  of  the  dorsal  valve  is  divided  by  a 
broad  delthyrium,  in  the  center  of  which  is  a  very  slightly  developed 
cardinal  process." — Walcott,  1912. 

Occurrence. — CONOCOCHEAGUE  LIMESTONE.  Near  Scotland,  Franklin 
County,  Pennsylvania,  and  the  same  horizon  near  Funkstown,  Maryland, 
furnish  fragments  apparently  of  this  species.  Upper  Canadian  and 
lowest  Ordovician  of  Utah,  New  Mexico  and  Colorado. 

Collections. — Maryland  Geological  Survey,  U.  S.  'National  Museum. 

Family  ORTHIDAE 

Genus  HEBERTELLA  Hall  and   Clarke 

HEBERTELLA  BOREALIS  (Billings) 

Plate  XXXVIII,  Figs.  9-12;  Plate  XLI,  Fig.  17 

OrtMs  borealis  Billings,  1859,  Canadian  Nat.  Geol.,  vol.  iv,  p.  436,  fig.  14. 
Orthis  borealis  Billings,  1863,  Geol.  Canada,  p.  129,  fig.  56,  p.  167,  fig.  148. 
Heltertella  borealis  Raymond,  1911,  Ann.  Carnegie  Mus.,  vol.  vii,  No.   2, 
p.  241,  text  figs.  13,  14. 

Description. — "  Shell  transversely  oval,  width  at  hinge  considerably 
less  than  the  width  below.  Sides  rounded,  front  straight  or  slightly 
rounded.  There  is  a  low,  broad  depression  in  both  valves.  The  pedicle 
valve  is  the  more  convex  of  the  two  in  young  specimens,  but  in  mature 
shells  the  brachial  valve  is  slightly  the  larger.  The  cardinal  area  of  the 
pedicle  valve  is  high  and  incurved,  with  a  narrow  delthyrium.  The  sur- 
face is  marked  by  from  20  to  30  broad,  simple  plications,  separated  by 
very  narrow  grooves." — Raymond,  1911. 

Occurrence. — STONES  EIVER  LIMESTONE  (Middle  division).  Near 
Maugansville,  Maryland;  Chambersburg,  Pennsylvania. 

CHAMBERSBURG  LIMESTONE  (Caryocystites  bed).  Fort  Loudon  and 
Blue  Spring,  Pennsylvania. 

A  not  uncommon  Chazyan  fossil  in  Canada  and  New  York.  In  east 
Tennessee  the  species  occurs  in  the  Lenoir  (Middle  Chazyan)  limestone. 

Collections. — Maryland  Geological  Survey,  U.  S.  National  Museum. 


MARYLAND  GEOLOGICAL  SURVEY  239 

HEBERTELLA  VULGARIS  Raymond 
Plate  XXXVIII,  Figs.  1-5;  Plate  XLI,  Fig.  18 

Hebertella  vulgaris  Raymond,  1911,  Ann.  Carnegie  Mus.,  vol.  vii,  No.  2, 
p.  242,  pi.  xxxvi,  figs.  2-5,  text  figs.  15-18,  22. 

Description. — "  Valves  nearly  equally  convex,  outline  transversely  oval, 
hinge  of  variable  length,  but  always  less  than  the  greatest  width.  Sides 
and  front  rounded.  Some  specimens  have  a  broad  shallow  sinus  in  the 
pedicle  valve,  while  others  have  that  valve  evenly  convex,  or  merely 
flattened  toward  the  front.  The  brachial  valve  usually  shows  a  narrow 
but  not  deep  sinus,  which  extends  from  the  beak  nearly  or  quite  to  the 
front.  The  line  in  which  the  two  valves  meet  is  usually  straight,  but  in 
those  specimens  which  have  a  sinus  in  the  pedicle  valve  and  not  in  the 
brachial,  the  front  is  sinuate.  Mature  specimens  usually  have  from  60  to 
90  fine  striae  on  each  valve.  The  striae  increase  both  by  bifurcation  and 
implantation.  The  cardinal  area  of  the  pedicle  valve  is  high  and  slightly 
incurved,  the  delfchyrium  apparently  open.  The  teeth  are  supported  by 
thin  lamellae,  between  which  are  the  scars  of  the  muscles.  In  the  brachial 
valve  there  is  a  low  median  septum  which  expands  at  the  posterior  end, 
forming  a  platform,  in  the  middle  of  which  is  the  small  linear  cardinal 
process.  In  front  of  this  platform  are  two  pairs  of  deep  adductor  scars. 
The  dental  sockets  are  narrow  and  deep." — Eaymond,  1911. 

Occurrence. — STONES  RIVER  LIMESTONE  (Middle  division).  Cham- 
bersburg,  Pennsylvania. 

CHAMBERSBURG  LIMESTONE  (Caryocystites  bed).  Fort  Loudon  and 
near  Blue  Spring,  Pennsylvania. 

An  abundant  fossil  in  the  Chazyan  rocks  of  New  York,  Canada,  and 
Tennessee. 

Collections. — Maryland  Geological  Survey,  U.  S.  National  Museum. 

HEBERTELLA  BELLARUGOSA  (Conrad) 
Plate  XLI,  Fig.  6 ;  Plate  XLV,  Figs.  10-12 

Orthis  bellarugosa  Conrad,  1843,  Proc.  Acad.  Nat.  Sci.,  Phila.,  vol.  i,  p.  333. 

Orthis  bellarugosa  Hall,  1847,  Pal.,  New  York,  vol.  i,  p.  118,  pi.  xxxii,  fig.  3. 

Orthis  (Hebertella  ?)  bellarugosa  Winchell  and  Schuchert,  1893,  Geol.  Min- 
nesota, vol.  ili,  p.  434,  pi.  xxxiii,  figs.  1-4. 

Hebertella  bellarugosa  Raymond,  1911,  Ann.  Carnegie  Mus.,  vol.  vii,  No.  2, 
p.  245,  pi.  xxxvi,  figs.  8,  9,  text  figs.  19,  20. 

16 


240  SYSTEMATIC  PALEONTOLOGY 

Description. — "  Shell  usually  nearly  circular  in  outline,  valves  about 
equally  convex.  Surface  marked  by  from  30  to  40  coarse  striae  which 
increase  by  implantation  and  bifurcation.  The  radial  striae  are  crossed 
by  sharp  concentric  lamellae,  producing  the  rugose  appearance  which 
suggested  the  specific  name.  From  10  to  15  of  the  radial  striae  are 
stronger  than  the  others,  and  between  each  pair  of  strong  striae  is  a 
single  weaker  one,  except  in  the  sinus  of  the  brachial  valve,  where  there 
are  two.  The  pedicle  valve  is  evenly  convex,  somewhat  flattened  toward 
the  front,  but  without  a  sinus.  Hinge  line  less  than  the  greatest  width. 
Cardinal  area  not  high,  nor  much  incurved.  The  bachial  valve  has  a 
narrow  median  sinus. 

"  The  shells  vary  in  outline ;  some  are  wider  than  long,  while  in  others 
the  width  and  length  are  about  equal.  The  sides  are  rounded,  and  the 
front  is  nearly  straight  in  some  specimens  and  rounded  in  others." — 
Eaymond,  1911. 

Occurrence. — CHAMBERSBURG  LIMESTONE  ( Caryocystites  and  Echino 
spherites  beds).     Pinesburg  and  Wilson,  Maryland:  Fort  Loudon  and 
Blue  Spring,  Pennsylvania. 

The  original  types  of  this  wide-spread  species  were  obtained  in  the 
Black  River  rocks  of  Wisconsin. 

Collections. — Maryland  Geological  Survey,  U.  S.  National  Museum. 

Genus  ORTHIS  Dalman 

ORTHIS  TRICENARIA  Conrad 

Plate  XLVII,  Figs.  4-6 

Orthis  tricenaria  Conrad,  1843,  Proc.  Acad.  Nat.  Sci.  Philadelphia,  vol.  i, 

p.  333. 

Orthis  tricenaria  Hall,  1847,  Pal.  New  York,  vol.  i,  p.  121,  pi.  xxxii,  fig.  8. 
Orthis  tricenaria.  Hall  and  Clarke,  1892,  Pal.  New  York,  vol.  viii,  pt.  1, 

pp.  191,  193,  221,  228,  pi.  v,  figs.  9-14. 
Orthis  tricenaria,  Weller,  1903,  Geol.  Surv.  New  Jersey,  Pal.,  vol.  iii,  p.  151, 

pi.  ix,  figs.  18-21. 

Description. — "  Shell  plano-convex,  longitudinally  semi-elliptical  in 
outline ;  hinge-line  equal  to  the  greatest  width  of  the  shell,  rarely  shorter. 
Cardinal  area  well  developed  on  each  valve.  Surface  marked  by  30  to  3fi 


MARYLAND  GEOLOGICAL  SURVEY  241 

usually  nearly  equal,  simple,  subangular,  radiating  costae,  which  are 
crossed  by  exceedingly  delicate,  concentric  lines  of  growth.  Pedicle  valve 
strongly  convex,  subangular  along  the  median  line,  with  the  greatest 
elevation  on  the  umbo.  Cardinal  area  very  high,  more  or  less  concave, 
striated  longitudinally  and  transversely,  divided  by  a  very  narrow  delthy- 
rium,  whose  apical  third  is  occupied  by  a  flat,  concave  or  convex  deltidium. 
Brachial  valve  nearly  flat,  slightly  elevated  at  the  beak,  from  which  point 
the  surface  slopes  gradually  into  a  broad,  scarcely  perceptible,  rarely  well- 
defined,  median  sinus.  Cardinal  area  nearly  one-third  as  wide  as  that  of 
the  pedicle  valve,  flat,  divided  by  a  triangular  delthyrium,  which  is  as 
broad  as  long  and  more  or  less  covered  by  a  convex  chilidium,  the  anterior 
margin  of  which  is  concave.  The  dimensions  of  a  rather  large  specimen 
are:  Length,  19  mm.;  width,  20  mm.;  thickness,  10.5  mm." — Weller, 
1903. 

A  characteristic  fossil  of  the  Black  Eiver  group  of  the  Mississippi  and 
Appalachian  valleys. 

Occurrence. — CHAMBERSBTJRG  LIMESTONE  (Mdulites  bed).  Wilson 
and  Pinesburg,  Maryland. 

Collections. — Maryland  Geological  Survey,  U.  S.  National  Museum. 

Genus  PLECTORTHIS  Hall  and   Clarke 
PLECTORTHIS  PLICATELLA  Hall 

Plate  LVII,  Figs.  4-7 

OrtMs  plicatella  Hall,  1847,  Pal.  New  York,  vol.  i,  p.  122,  pi.  xxxii,  fig.  9. 
OrtMs  plicatella  Meek,  1873,  Pal.  Ohio,  vol.  i,  p.  108,  pi.  viii,  fig.  7. 
Plectortttis  plicatella  Hall  and  Clarke,  1892,  Pal.  New  York,  vol.  viii,  pt.  i, 
p.  22,  pi.  v,  figs.  18-20. 

Description. — "  Broadly  semiov'al,  nearly  equivalve,  length  and  breadth 
about  as  3  to  4;  surface  marked  by  strong  radiating  plicae,  which  are 
usually  simple,  about  20  to  28  on  each  valve,  crossed  by  simple  elevated 
concentric  lines,  which  are  more  distinct  in  the  depressions  between  the 
costae,  and  often  obscure  or  obsolete  upon  their  exposed  surfaces;  valves 
nearly  equally  convex,  without  sensible  depression  or  elevation  on  either 
one,  meeting  at  the  edges  in  a  straight  line ;  cardinal  line  not  extending 


242  SYSTEMATIC  PALEONTOLOGY 

beyond  the  width  of  the  shell;  area  narrow,  dorsal  foramen  extending 
to  the  beak."— Hall,  1847. 

Occurrence. — MARTIXSBURG  SHALE  (Orthorhynchula  bed  at  the  top  of 
the  Fairview  division).  Tuscarora  Mountain,  one  and  one-half  miles 
southeast  of  McConnellsburg,  Pennsylvania.  The  types  of  this  species 
were  obtained  in  the  upper  part  of  the  Fairview  formation  at  Cincinnati, 
Ohio. 

Collections. — Maryland  Geological  Survey,  U.  S.  National  Museum. 

PLECTORTHIS  PLICATELLA  Hall  var. 
Plate  LIV,  Figs.  15-16 

Description. — The  typical  form  of  this  species  occurs  in  the  lower  part 
of  the  Maysville  group  at  Cincinnati,  Ohio,  and  vicinity.  The  upper  part 
of  the  Martinsburg  shale  in  Pennsylvania  has  afforded  brachiopod  so 
close  to  P.  plicatella  that  it  cannot  be  considered  more  than  a  variety. 
Unfortunately  the  preservation  of  these  specimens  is  not  good  enough  to 
allow  this  variety  to  be  distinguished.  A  description  of  Plectorthis 
plicatella  is  given  above. 

Occurrence. — MARTINSBURG  SHALE  (Eden  division).  Jordans  Knob, 
one  and  one-half  miles  northeast  of  Fort  Loudon,  Pennsylvania,  has  fur- 
nished the  Eden  form  here  regarded  as  a  variety. 

Collections. — Maryland  Geological  Survey,  U.  S.  National  Museum. 

Genus  DALMANELLA  Hall  and  Clarke 
DALMANELLA  TESTUDINARIA  (Dalman)  var. 

Plate  L,  Figs.  9,  10 

Orthis  testudinaria  Dalman,  1828,  Kongl.  Sverrska  Vet.-Akad.  Handl.,  p.  115, 

pi.  ii,  fig.  4. 
Dalmanella  testudinaria  Weller,  1903,  Geol.  Surv.  New  Jersey,  Pal.,  vol.  iii, 

p.  155,  pi.  x,  figs.  1,2;  p.  216,  pi.  xvi,  figs.  4,  5. 

Description. — "  Adult  shells  subcircular  and  the  younger  ones  trans- 
versely subelliptical  in  outline;  hinge-line  less  than  the  greatest  width: 
cardinal  angles  rounded,  lateral  and  anterior  margins  broadly  rounded, 
though  the  extreme  front  of  the  shell  is  sometimes  straight  for  a  short 


MARYLAND  GEOLOGICAL  SURVEY  243 

distance.  Surface  of  both  valves  marked  by  unequal,  angular,  radiating 
costae,  about  10  or  12  of  the  largest  ones  having  their  origin  at  the  beak, 
the  remainder  being  lateral  branches  from  these.  In  some  of  the  larger 
individuals  as  many  as  60  or  more  costae  are  present  along  the  margin 
of  the  shell.  The  branches  from  the  main  costae  are  small  at  first,  but 
increase  in  size  towards  the  margin  of  the  shell,  and  themselves  give  off 
additional  branches.  In  many  individuals  this  manner  of  branching  gives 
to  the  costae  a  more  or  less  fasciculate  appearance,  each  fascicle  having 
one  large  rib  in  the  center,  with  smaller  ones  on  either  side.  In  those 
specimens  having  the  shell  well  preserved  the  bottoms  of  the  grooves 
between  the  costae  exhibit  a  series  of  fine,  transverse  crenulations. 
Pedicle  valve  convex,  subcarinate  along  the  median  line,  the  lateral  slopes 
nearly  straight,  the  greatest  convexity  of  the  valve  about  one-third  the 
distance  from  the  beak.  Cardinal  area  moderately  concave,  forming  an 
angle  of  about  45°  with  the  plane  of  the  valve,  about  five  or  six  times  as 
high.  Delthyrium  a  little  higher  than  wide.  Brachial  valve  nearly  flat, 
with  a  sinus  beginning  close  to  the  beak  and  expanding  in  a  broad,  shallow 
depression  towards  the  front. 

"  The  dimensions  of  an  average-sized  specimen  are :  Length,  8  mm. ; 
width,  8.25  mm. ;  convexity  of  pedicle  valve,  2.5  mm." — Weller,  1903. 

The  particular  variety  of  Dalmanella  testudinaria  described  above  by 
Weller  from  the  Trenton  limestone  of  New  Jersey  is  represented  in  the 
Sinuites  bed  at  the  base  of  the  Martinsburg  shale. 

Occurrence. — MARTINSBURG  SHALE  (Sinuites  bed).  The  Trenton 
variety  here  figured  occurs  at  Chambersburg,  Pennsylvania,  and  Stras- 
burg,  Virginia.  Shells  identified  as  this  species  occurs  in  most  of  the 
Middle  and  Upper  Ordovician  strata  of  Europe  and  America. 

Collections. — Maryland  Geological  Survey,  U.  S.  National  Museum. 

DALMANELLA  EDSONI  n.  sp. 

Plate  XLIX,  Figs.  17-21 

Description. — This  well-marked  new  species  is  distinguished  by  its 
large  size  and  by  its  sharply  folded  plications,  arranged  in  bundles.  The 
length  and  breadth  of  average  specimens  from  southern  Pennsylvania  is 


244  SYSTEMATIC  PALEONTOLOGY 

as  3  is  to  4.  mm.,  that  is,  the  length  is  18  mm.  and  the  breadth  24  mm. 
Other  specimens  from  the  same  area  attain  as  great  a  breadth  as  35  mm. 
The  Vermont  specimens  are  even  more  robust,  an  average  specimen  here 
being  30  mm.  long  and  almost  40  mm.  broad.  The  arrangement  of  the 
plications  in  bundles,  each  bundle  being  marked  off  by  a  stronger  plica- 
tion, is  also  a  striking  specific  feature.  The  specific  name  is  in  honor  of 
the  late  George  E.  Edson,  who  discovered  the  species  in  the  Trenton 
rocks  of  Vermont. 

Occurrence. — MARTINSBURG  SHALE  (Sinuites  bed).  Two  miles  south 
of  St.  Thomas,  Pennsylvania.  Lower  Trenton  at  Highgate  Springs,  Ver- 
mont. 

Collection. — U.  S.  National  Museum. 

DALMANELLA  MULTISECTA  (Meek) 
Plate  LIV,  Figs.  5,  G 

Orthis  emacerata  var.  multisecta  (James  MSS.)  Meek,  1873,  Pal.  Ohio,  vol.  i, 

p.  112,  pi.  viii,  fig.  3. 
Orthis  emacerata  var.  multisecta  Miller,  1875,  Cincinnati  Quart.  Jour.  Sci., 

vol.  ii,  p.  22. 
Orthis  multisecta  Sardeson,  1897,  American  Geologist,  vol.  xix,  p.  97,  pi.  iv, 

figs.  20-23. 
Dalmanella  testudinaria  var.   multisecta  Cumings,   1908,   32d   Ann.   Rept. 

Dept.  Geol.  and  Nat.  Res.  Indiana,  p.  901,  pi.  xxxiii,  figs.  4,  4c. 

Description. — "  Shell  small,  subcircular,  plano-convex,  or  sometimes 
concavo-convex,  hinge  line  shorter  than  the  greatest  breadth  of  the  valves ; 
valves  thin.  Dorsal  valve  nearly  flat,  or  having  a  concentric  depression 
through  the  middle;  mesial  sinus  undefined  or  indistinct;  beak,  small, 
not  incurved;  area  low  at  the  middle,  and  narrowing  off  to  nothing  at 
the  lateral  extremities;  foramen  very  small  and  filled  by  the  cardinal 
process.  Interior  flat ;  mesial  ridge  extending  to  about  the  middle  of  the 
shell,  without  any  well-defined  termination;  scars  of  posterior  pair  of 
adductor  muscles  a  little  smaller  than  the  anterior  pair,  from  which  they 
are  separated  by  a  very  fine  line,  or,  more  generally,  not  distinctly  sepa- 
rated; cardinal  process  very  small,  conical,  obscurely  trifid  on  the  pos- 


MARYLAND  GEOLOGICAL  SURVEY  245 

terior  side;  brachial  processes  slender,  prominent,  and  directed  obliquely 
forward ;  surface  granular  and  showing  the  radiating  striae. 

"  Ventral  valve  convex,  with  elevated  mesial  ridge,  greatest  convexity 
just  behind  the  middle;  beak  arched,. projecting  slightly;  area  moderate, 
narrowing  laterally;  foramen  an  equilateral  triangle,  partly  occupied  by 
the  cardinal  process  of  the  other  valve.  Interior  strongly  concave,  show- 
ing moderately  prominent  teeth ;  dental  laminae  extend  from  the  base  of 
the  teeth  forward,  gradually  becoming  more  indistinct  as  they  fade  away 
in  a  circular  line  to  the  mesial  depression,  forming  a  heart-shaped  cavity 
for  the  muscular  scars;  surface  granular  and  showing  the  radiating 
striae. 

"  Surface  of  both  valves  ornamented  by  fine  radiating  striae,  that 
increase  by  bifurcation ;  lateral  striae  curved  so  that  a  few  of  them  run 
out  on  the  hinge  line;  concentric  striae  plainly  visible  with  the  aid  of  a 
magnifier,  and  sometimes  visible  to  the  unaided  eye;  imbricating  marks 
of  growth  usual.  Length  of  an  average  full-grown  specimen,  0.50  inch; 
breadth,  0.58  inch;  convexity,  0.20  inch.  They  vary,  however,  from  one- 
fourth  this  size  to  one-half  larger." — Miller,  1875. 

This  is  probably  the  most  abundant  fossil  of  the  Eden  shale  wherever 
exposed.  In  the  Appalachian  Valley  of  Pennsylvania  and  Maryland  it 
occurs  in  the  upper  sandy  layers  of  the  Martinsburg. 

Occurrence. — MARTINSBURG  SHALE  (Eden  division).  Jordans  Knob, 
one  and  one-half  miles  northeast  of  Fort  Loudon,  in  Pennsylvania,  and  the 
west  slope  of  Eickard  Mountain  in  Maryland  furnish  specimens. 

Collections. — Maryland  Geological  Survey,  U.  S.  National  Museum. 

DALMANELLA  ELECTRA  (Billings) 

Plate  XXXV,  Fig.  6 

Orthis  electro,  Billings,  1865,  Pal.  Foss.,  vol.  i,  p.  79,  fig.  72. 
Dalmanella  electro,  Weller,  1903,  Geol.  Surv.  New  Jersey,  Pal.,  vol.  iii,  p.  125, 
pi.  iv,  fig.  13. 

Description. — Shell  wider  than  long,  the  usual  dimensions  being  about 
6  mm.  in  length  and  7  mm.  in  width,  with  the  hinge-line  a  little  shorter 
than  the  greatest  width,  and  the  cardinal  extremities  angular.  Pedicle 


246  SYSTEMATIC  PALEONTOLOGY 

valve  moderately  convex  on  the  umbo,  but  more  flattened  towards  the 
cardinal  extremities;  cardinal  area  narrow,  concave  above;  beak  project- 
ing slightly  beyond  the  cardinal  margin.  Surface  marked  by  about  50 
fine,  subequal,  radiating  costae,  increasing  by  bifurcation. 

The  numerous  fine  radiating  costae  distinguish  this  shell  from  the 
closely  allied  Dalmanella  wemplei  Cleland,  which  differs  in  having  larger 
costae  at  regular  intervals. 

Occurrence. — BEEKMANTOWN  LIMESTONE  (Ceratopea  zone).  West  of 
Hagerstown,  near  Halfway,  and  east  of  Williamsport,  Maryland. 

Canadian  at  Point  Levis,  Quebec,  Newfoundland,  New  Brunswick, 
New  Jersey  and  Pennsylvania. 

Collections. — Maryland  Geological  Survey,  U.  S.  National  Museum. 

DALMANELLA  WEMPLEI  Cleland 
Plate  XXXI,  Figs.  7-12 

Dalmanella  (Orthis)  wemplei  Cleland,  1900,  Bull.  Amer.  Pal.,  vol.  iii,  p.  129 

(257),  pi.  xvii,  figs.  10-13. 
Dalmanella  wemplei  Weller,  1903,  Geol.   Surv.  New  Jersey,  Pal.,  vol.  iii, 

p.  124,  pi.  iv,  figs.  10-12. 
Dalmanella  wemplei  Cleland,  1903,  Bull.  Amer.  Pal.,  vol.  iv,  p.  19. 

Description,. — Shell  small,  the  average  being  about  5  mm.  long  and 
6  mm.  wide,  subquadrangular  to  subcircular  in  outline,  with  the  hinge- 
line  slightly  shorter  than  the  width;  cardinal  extremities  usually  quite 
angular.  Pedicle  valve  strongly  convex,  highest  posterior  to  the  middle ; 
beak  elevated,  projecting  beyond  the  hinge-line;  cardinal  area  high, 
slightly  arched.  Brachial  valve  much  less  convex  than  the  pedicle,  with 
a  mesial  depression  which  may  become  a  shallow  sinus  towards  the  front. 
Surface  of  each  valve  marked  by  from  10  to  16  stronger,  radiating  costae, 
alternating  with  from  two  to  four  finer  ones. 

This  species  differs  from  the  closely  related  Dalmanella  electra  (Bill- 
ings) which  occurs  in  the  higher  beds  of  the  Beekmantown,  especially 
in  its  coarser  striae  which  alternate  with  from  two  to  four  finer  ones. 

The  original  types  were  collected  in  the  Tribes  Hill  limestone  at  Fort 
Hunter,  New  York.  The  species  has  been  identified  by  Weller  in  the 


MARYLAND  GEOLOGICAL  SURVEY  247 

corresponding  horizon  in  the  Canadian  part  of  the  Kittatinny  limestone 
at  Columbia,  New  Jersey.  Specimens  fairly  well  preserved  are  not 
uncommon  in  the  Stonehenge  limestone,  particularly  the  upper  part,  at 
many  localities  in  Maryland.  The  outcrops  around  Hagerstown  and 
Funkstown  have  shown  some  layers  fairly  crowded  with  this  brachiopod. 

Occurrence. — BF.EKMANTOWN  LIMESTONE  (Stonehenge  member). 
Numerous  localities  in  Maryland,  especially  around  Hagerstown  and 
Funkstown.  Tribes  Hill  limestone  at  Fort  Hunter,  New  York,  and  Kit- 
tatinny limestone,  Columbia,  New  Jersey. 

Collections. — Maryland  Geological  Survey,  U.  S.  National  Museum. 

Family  RHIPIDOMELLIDAE 

Genus  DINORTHIS  Hall  and  Clarke 

DINORTHIS  (PLAESIOMYS)  PLATYS  (Billings) 

Plate  XXXVIII,  Figs.  6-8 

Orthis  platys  Billings,  1859,  Canadian  Nat.  and  Geol.,  vol.  iv,  p.  438,  fig.  15. 
Dinorthis  platys  Schuchert,  1897,  Bull.  U.  S.  Geol.  Surv.,  87,  p.  216. 
Plaesiomys  platys  Raymond,  1911,  Ann.  Carnegie  Mus.,  vol.  vii,  No.  2,  p.  238, 
pi.  xxxv,  figs.  13,  14. 

Description. — "  Pedicle  valve  fairly  high  and  convex  on  the  umbo, 
flat  or  only  slightly  convex  in  front.  Brachial  valve  nearly  flat,  usually 
showing  a  shallow  sinus  on  the  umbo.  Surface  marked  by  fairly  coarse 
striae,  which  increase  by  implantation.  There  are  usually  three  or  four 
in  the  space  of  2  mm.  on  the  front  of  the  shell.  The  interior  of  the 
pedicle  valve  shows  a  small  muscle  area  under  the  beak,  composed  of  two 
strong  diductor  scars,  and  between  them  two  very  narrow  adductor  scars. 
Delthyrium  narrow.  No  specimen  has  been  seen  which  was  so  preserved 
as  to  retain  the  deltidium.  In  the  brachial  valve  there  is  a  low  median 
septum.  Other  details  could  not  be  made  out." — Raymond,  1911. 

Occurrence. — STONES  RIVER  LIMESTONE  (Middle  division).  Maugaus- 
ville,  Maryland. 

The  types  occurred  in  the  Chazyan  at  Montreal,  Canada.  In  the  Lake 
Champlain  area  this  fossil  occurs  in  the  Crown  Point  or  middle  division 


248  SYSTEMATIC  PALEONTOLOGY 

of  the  Chazyan.    In  east  Tennessee  it  is  found  in  the  supposedly  equiva- 
lent horizon — the  Lenoir  limestone. 

Collections. — Maryland  Geological  Survey,  U.  S.  National  Museum. 

DINOETHIS  PECTINELLA  (Emmons) 
Plate  XLV,  Figs.  8,  9 

Orthis  pectinella  Emmons,  1842,  Geol.  New  York,  Rep.  2d  Dist,  p.  394,  fig.  2. 

Dinorthis  pectinella  Hall  and  Clarke,  1892,  Pal.  New  York,  vol.  viii,  pt.  1, 
pp.  195,  222,  228,  pi.  v,  figs.  27-33. 

Orthis  (Dinorthis)  pectinella  Winchell  and  Schuchert,  1893,  Geol.  Minne- 
sota, vol.  iii,  p.  424,  pi.  xxxii,  figs.  31-34. 

Dinorthis  pectinella  Weller,  1903,  Geol.  Surv.  New  Jersey,  Pal.,  vol.  iii, 
p.  154,  pi.  ix,  figs.  29,  30. 

Description. — "  Shell  resupinate,  transversely  subelliptical  in  outline, 
wider  than  long,  in  about  the  proportion  of  four  to  three;  cardinal  line  is 
usually  less  than  the  greatest  width  of  the  shell,  the  cardinal  extremities 
rounded;  surface  of  each  valve  marked  by  from  22  to  30  prominent, 
rounded,  simple  costae,  which  are  equal  in  width  to  the  spaces  between, 
and  are  crossed  by  fine,  closely  crowded  elevated,  concentric  lines  of 
growth.  Pedicle  valve  slightly  convex  near  the  beak,  flattened  on  the 
sides,  with  a  broad,  shallow,  ill-defined  depression  along  the  center, 
usually  most  distinct  in  front,  but  frequently  nearly  obsolete.  Cardinal 
area  moderately  large  and  well  defined,  flat,  lying  nearly  at  right  angles 
to  the  plane  of  the  shell.  Brachial  valve  regularly  convex,  most  prominent 
in  the  center,  flattened  and  slightly  deflected  near  the  cardinal  extremi- 
ties. Cardinal  area  much  narrower  than  that  of  the  opposite  valve,  lying 
nearly  in  the  plane  of  the  shell. 

"  The  dimensions  of  the  nearly  perfect  pedicle  valve  are :  Length, 
21  mm.;  width,  27.5  mm."— Weller,  1903. 

Occurrence. — CHAMBERSBUEG  LIMESTONE  (Echinospherites  bed). 
Wilson  and  Pinesburg,  Maryland. 

This  species  occurs  in  the  Upper  Black  River  and  Early  Trenton  of 
New  York  and  Canada,  and  the  Ohio  and  Mississippi  valleys. 

Collections. — Maryland  Geological  Survey,  TJ.  S.  National  Museum. 


MARYLAND  GEOLOGICAL  SURVEY  249 

Genus  PIANODEMA  Foerste 

PlANODEMA  SUBAEQUATA   (Conrad) 

Plate  XLV,  Figs.  1-3 

Orthis  subaequata  Conrad,  1843,  Proc.  Acad.  Nat.  Sci.  Philadelphia,  vol.  i, 
p.  333. 

Dalmanella  subaequata  Hall  and  Clarke,  1892,  Pal.  New  York,  vol.  viii,  pt.  1, 
pp.  194,  207,  224,  pis.  5c,  figs.  6-11. 

Orthis  (Dalmanella)  subaequata  Winchell  and  Schuchert,  1893,  Geol.  Min- 
nesota, vol.  iii,  p.  446,  pi.  xxxiii,  figs.  30-36. 

Dalmanella  subequata  Weller,  1903,  Geol.  Surv.  New  Jersey,  Pal.,  vol.  iii, 
p.  156,  pi.  x,  figs.  3,  4. 

Description. — "  Shell  subequally  biconvex,  usually  wider  than  long ; 
the  hinge-line  shorter  than  the  greatest  width  of  the  shell,  except  some- 
times in  young  individuals;  cardinal  extremities  angular  or  rounded. 
Surface  of  each  valve  marked  by  numerous,  fine,  tubulose  striae,  which 
bifurcate  about  twice  in  passing  from  the  beak  to  the  anterior  margin. 
Pedicle  valve  strongly  and  evenly  convex,  the  greatest  elevation  posterior 
to  the  middle  of  the  shell;  near  the  beak  and  upon  the  umbo  no  medial 
depression  exists,  but  near  the  middle  of  the  valve  a  broad,  shallow  and 
indistinct  sinus  begins  and  becomes  deeper  toward  the  anterior  margin. 
The  cardinal  area  is  well  defined,  broadly  triangular,  elevated  and  only 
moderately  concave;  the  delthyrium,  with  slightly  curved  sides,  is  about 
t\\dce  as  high  as  wide.  Brachial  valve  more  evenly,  but  a  little  less  convex 
than  the  pedicle,  the  greatest  elevation  near  the  middle.  Near  the  beak 
the  mesial  portion  of  the  shell  is  usually  flattened  or  slightly  depressed, 
but  near  the  middle  of  the  shell  this  flattening  gradually  changes  into  a 
low,  broad,  ill-defined  elevation,  corresponding  with  the  sinus  of  the 
pedicle  valve.  The  cardinal  area  is  narrow  and  concave,  with  a  delthy- 
rium as  broad  or  broader  than  high.  The  dimensions  of  an  average  speci- 
men are :  Breadth,  16  mm.,  and  length,  14  mm." — Weller,  1903. 

Occurrence. — CHAMBERSBURG  LIMESTONE  (Echinospherites  bed). 
Pinesburg  Station,  Maryland,  and  various  localities  in  southern  Penn- 
sylvania. Stones  Eiver  group  of  Tennessee  and  the  Black  Eiver  group 
of  Minnesota,  etc. 

Collections. — Maryland  Geological  Survey,  U.  S.  National  Museum. 


250  SYSTEMATIC  PALEONTOLOGY 

Superfamily  STROPHOMENACEA 

Family  STROPHOMENIDAE 

Genus  STROPHOMENA  Blainville 

STROPHOMENA  STOSEI  n.  sp. 

Plate  XXXVII,  Figs.  1-4 

Description. — This  brachiopod,  which  is  the  most  frequent  fossil  of 
the  few  species  discovered  in  the  Frederick  limestone  is  known  from 
both  brachial  and  pedicle  valves,  although  none  show  the  hinge  line 
clearly.  Its  general  shape  is  that  of  Strophomena  sinuata  James  of  the 
Cincinnatian  rocks,  but  8.  stosei  differs  conspicuously  in  the  occurrence 
of  several  fine  radiating  striae  between  each  of  the  larger  coarse  ones. 
The  interior  of  the  brachial  valve  in  each  of  these  species  seems  to  be 
quite  alike  and  the  reference  of  this  new  species  of  .Strophomena  to  the 
8.  sinuata  group  appears  to  be  warranted. 

The  specific  name  is  in  honor  of  George  W.  Stose,  of  the  U.  S.  Oeo- 
logical  Survey,  who  helped  collect  the  type  specimens. 

Occurrence. — FREDEKICK  LIMESTONE.  Just  east  of  Frederick,  Mary- 
land. 

Collections. — Maryland  Geological  Survey,  U.  S.  National  Museum. 

STROPHOMENA  SCULPTURATA  n.  sp. 
Plate  XLIX,  Fig.  1 

Description. — Although  this  new  species  belongs  to  a  group  of  brachio- 
pods  not  uncommon  in  the  faunas  of  eastern  North  America,  all  of  these 
species  happen  to  be  new,  so  that  comparison  is  not  necessary.  It  is  the 
only  brachiopod  in  the  Middle  Ordovician  limestone  with  such  a  highly 
sculptured  shell  and  for  that  reason  will  be  easily  recognized.  Between 
each  of  the  very  distinct  radiating  ridges  there  are  five  or  six  smaller 
radiating  striae  visible  only  under  a  lens.  Transverse  to  these  radiating 
striations  are  concentric,  squamose  ridges  of  growth  quite  similar  to  those 
obtaining  in  Leptaena  charlottae.  In  the  latter  respect  the  group  of 
species  is  related  to  Leptaena,  but  other  features  suggest  Stropliomena. 

An  average  specimen  is  10  mm.  high  and  13  mm.  wide. 


251 

Occurrence. — MARTINSBURG  SHALE  (Sinuites  bed).  Pennsylvania. 
The  type  specimens  are  from  one  mile- south  of  St.  Thomas. 

Collections. — Maryland  Geological  Survey,  IT.  S.  National  Museum. 

STROPHOMENA  HALLIE  (S.  A.  Miller) 
Plate  LIV,  Figs.  7-9 

Streptorhynchus  ?  hallie  Miller,  1874,  Cincinnati  Quart.  Jour.  Sci.,  vol.  i, 

p.  148,  figs.  14-16. 
Strophomena  hallie  Foerste,  1914,  Bull.  Sci.  Lab.  Denison  Univ.,  vol.  xvii, 

p.  38,  pi.  ii,  figs.  la-e. 

Description. — "  Shell  sub-trigonal  in  outline,  concavo-convex,  deflected 
laterally,  resupinate,  rather  thin  and  frail;  hinge  scarcely  equalling  the 
greatest  breadth  of  the  valves;  length  and  breadth  about  three-fourths 
of  an  inch. 

"  Dorsal  valve  convex  in  the  central  part,  flattened  on  the  umbone  and 
deflected  laterally ;  surface  marked  by  moderately  coarse,  radiating  striae, 
which  increase  by  intercalation  of  smaller  •  ones ;  area  linear,  beak  not 
distinct  from  the  edge  of  the  area.  Interior  showing  cardinal  process  to 
be  very  small  and  divided  into  two  teeth-like  parts,  directed  a  little 
forward  and  flattened  on  their  faces;  socket-ridges  small,  short,  and 
oblique;  mesial  ridge  scarcely  perceptible  without  a  magnifier,  radiating 
striae  plainly  visible. 

"  Ventral  valve  moderately  concave  in  the  central  and  anterior  regions, 
but  slightly  convex  at  the  beak,  which  is  perforated  and  projects  slightly 
beyond  the  edge  of  the  area;  surface  marked  by  radiating  striae,  which 
increase  by  even  bifurcations ;  area  narrow  and  sloping  laterally ;  foramen 
closed  by  a  rounded  deltidium  for  the  reception  of  the  cardinal  teeth  of 
the  dorsal  valve.  Interior  showing  trigonal  hinge  and  circular  cavity; 
marked  by  radiating  striae." — Miller,  1874. 

Occurrence. — MARTINSBUBG  SHALE  (Eden  division).  Jordans  Knob 
one  and  one-half  miles  northeast  of  Fort  Loudon,  and  Tuscarora  Moun- 
tain, two  and  one-half  miles  southeast  of  McConnellsburg,  Pennsylvania. 
Eden  shale  at  Cincinnati,  Ohio. 

Collection. — U.  S.  National  Museum. 


252  SYSTEMATIC  PALEONTOLOGY 

STROPHOMENA  SINUATA  James 

Plate  LIV,"  Figs.  10-14 

Strophomena  sinuata  James,  1871,  Cat.  Fossils,  Cincinnati  group,  p.  9. 
Strophomena  (Hemipronites)   sinuata  Meek,  1873,  Pal.  Ohio,  vol.  i,  p.  87, 

pi.  15,  fig.  5a-g. 
Strophomena  sinuata  Foerste,  1912,  Bull.  Sci.  Lab.  Denison  Univ.,  vol.  xvii, 

p.  57,  pi.  i,  figs.  3a-d. 

Description. — "  Shell  semicircular,  or  forming  rather  more  than  a 
semicircle,  moderately  convex,  with  valves  nearly  equal,  the  dorsal  being 
most  convex  in  the  central  and  anterior  regions,  and  the  ventral  near 
the  Timbo;  hinge  nearly  or  quite  equalling  the  greatest  breadth;  lateral 
margins  forming  more  or  less  nearly  right  angles  with  the  hinge  line; 
or  sometimes  rounding  a  little  to  the  same,  and  rounding  regularly  to  the 
front,  which  forms  a  semicircular  curve,  with  rarely  a  slight  sinuosity 
at  the  middle. 

"  Dorsal  valve,  flat  at  the  beak,  which  is  not  distinct  from  the  cardinal 
margin,  usually  a  little  raised  in  the  middle  at  the  front,  so  as  to  form  a 
low,  broad,  undefined  medial  prominence;  cardinal  area  narrow  and 
inclined  backward;  interior  with  a  low,  small,  deeply  bipartite  cardinal 
process,  from  which  diverge  three  small  ridges,  the  two  lateral  of  which 
extend  obliquely  outward  to  form  the  margins  of  the  rather  well-defined 
sockets  for  the  reception  of  the  teeth  of  the  other  valve,  while  the  third 
ridge  is  central,  and  extends  a  short  distance  forward;  muscular  scars 
not  visible  in  any  specimen  examined. 

"Ventral  valve  moderately  convex  at  the  umbo,  which  is  not  very 
prominent  or  arched,  and  has  a  minute  perforation  at  the  apex;  front 
with  usually  a  broad,  shallow,  undefined  depression ;  lateral  regions  more 
or  less  nearly  flat;  cardinal  area  well  developed,  tapering  to  the  lateral 
extremities,  flat,  and  inclined  more  or  less  obliquely  backward ;  foramen 
closed  by  a  prominent,  triangular  deltidium;  interior  showing  small, 
somewhat  saucer-shaped  cavity,  formed  by  the  low,  sharp  dental  laminae, 
extending  forward  from  the  inner  side  of  the  rather  well-developed 
oblique  cardinal  teeth,  and  curving  a  little  toward  each  other,  without 


MARYLAND  GEOLOGICAL  SURVEY  253 

meeting  at  their  inner  ends ;  muscular  scars  not  visible  in  any  specimens 
examined. 

"  Surface  of  both  valves  ornamented  with  rather  coarse  radiating 
striae,  most  of  which  bifurcate  once  or  oftener,  while  occasionally  a 
shorter  one  is  intercalated  between  two  longer ;  crossing  the  whole,  occa- 
sional small  marks  of  growth,  and  finer  but  obscure,  concentric  striae 
may  be  seen,  by  the  aid  of  a  lens,  on  well-preserved  specimens. 

"Length  of  a  rather  large  specimen,  0.65  inch;  breadth,  0.88  inch; 
convexity,  0.30  inch." — Meek,  1873. 

Occurrence. — MARTINSBURG  SHALE  (Eden  division).  Jordans  Knob, 
one  and  one-half  miles  northeast  of  Fort  Loudon,  and  Tuscarora  Moun- 
tain, two  and  one-half  miles  southeast  of  McConnellsburg,  Pennsylvania. 

This  species  has  hitherto  been  recorded  only  from  the  upper  part  of 
the  Fairview  formation  in  the  Ohio  Valley. 

Collections. — Maryland  Geological  Survey,  U.  S.  National  Museum. 

Genus  PLECTAMBONITES  Pander 

PLECTAMBONITES  PISUM  Euedemann 

Plate  XLVIII,  Figs.  1-7 

Plectambonites  pisum  Ruedemann,   1902,  Bull.  New  York  State  Museum, 
No.  49,  p.  19,  pi.  i,  figs.  8-20. 

Description. — "  Shell  small,  semicircular  in  outline,  with  subauricu- 
late  cardinal  extensions ;  highly  concavo-convex,  the  convexity  surpassing 
that  of  a  hemisphere;  toward  the  cardinal  ears  becoming  depressed  con- 
vex ;  length  to  width  as  4:5;  greatest  width  along  the  hinge  line,  which 
is  nearly  straight.  Surface  marked  with  very  fine  striae,  which  usually 
are  interrupted  by  from  16  to  20  coarse  striae;  sometimes  the  fine  striae 
become  nearly  obsolete,  leaving  the  interspace  between  the  coarse  striae 
almost  smooth;  at  other  times  the  coarse  striae  disappear,  leaving  the 
shell  uniformly  and  finely  striated ;  a  few  concentric  growth  lines  are  also 
present.  Pedicle  valve  extremely  gibbous,  the  greatest  elevation  being 
in  the  central  part;  the  unbonal  part  sloping  abruptly;  the  umbo  being 


254  SYSTEMATIC  PALEONTOLOGY 

protuberant  and  projecting  beyond  the  cardinal  line;  anterior  and  lateral 
slopes  less  abrupt,  near  the  margins  turning  suddenly  into  a  natter  border. 
Cardinal  area  moderately  elevated,  concave,  delthyrium  large,  of  equal 
width  and  length;  no  deltidium  observed.  Teeth  small,  supported  by 
strong,  diverging  dental  lamellae,  which  continue  in  outward  direction 
into  the  much  elevated  margin  of  the  diductor  muscles;  this  margin 
extends  about  one-fourth  the  length  of  the  valve,  and  then  returns  under 
an  acute  angle  including  a  very  deep  pyriform  muscle  pit.  The  muscle 
margins  are  separated  by  a  distinct  septum,  which  extends  to  near  the 
anterior  margin;  from  the  anterior  part  of  the  muscular  impressions 
extend  strongly  marked  vascular  trunks  which  are  tri-  or  quadripartite 
and  inclose  between  them  a  narrow  elongate  depressed  area.  Brachial 
valve  concave  in  the  middle  part,  closely  following  the  curvature  of  the 
pedicle  valve  with  a  well-defined  ridge  all  around  the  lateral  and  anterior 
margin.  Cardinal  area  as  high  as  that  of  the  pedicle  valve,  and  also 
slightly  concave,  retrorse,  with  a  large  chilidium,  somewhat  concave  in 
the  middle.  Cardinal  process  single  and  erect  and,  by  the  coalescence 
with  the  divergent,  short,  crural  plates,  appearing  distinctly  trilobate  at 
the  posterior  end,  similarly  to  P.  sericeus,  with  the  difference,  however, 
that  the  posterior  ends  of  the  crural  plates  are  not  closely  appressed  to 
the  cardinal  process,  but  separate  again  a  little,  forming  processes  almost 
as  prominent  as  and  parallel  to  the  cardinal  process.  Adductor  scars 
shallow,  broadly  triangular,  extending  not  quite  to  the  middle  of  the 
shell,  slightly  divergent,  inner  margins  formed  by  two  ridges,  branching 
from  the  crural  processes  and  extending  to  near  the  anterior  margin; 
outer  somewhat  indented  margin  of  the  muscular  impressions  greatly 
elevated  as  in  P.  gibbosus  Winchell  and  Schuchert. 

"  Dimensions :  Length,  8.5  mm. ;  width,  10.2  mm. ;  height,  5.5  mm."- 
Euedemann,  1902. 

Occurrence. — CHAMBEESBUKG  LIMESTONE  (Christiania  bed).     Penn- 
sylvania, Maryland,  and  Virginia. 

Kysedorph  conglomerate  at  base  of  Trenton,  New  York. 

Collections. — Maryland  Geological  Survey,  U.  S.  National  Museum. 


MARYLAND  GEOLOGICAL  SURVEY  255 

PLECTAMBONITES  RUGOSTJS  (Meek) 
Plate  LIV,  Figs.  31-33 

Leptaena  sericea  var.  rugosa  Meek,  1873,  Pal.   Ohio.  vol.  i,  pt.  2,  pi.  v, 

figs.  3f-h. 
Plectambonites  rugosa  Foerste,  1912,  Bull.   Sci.  Lab.  Denison  University, 

vol.  xvii,  p.  123,  pi.  i,  figs.  7a-c;  pi.  x,  figs.  7a-d. 

Description. — The  form  of  Plectambonites  found  so  abundantly  in  the 
Eden  shales  of  the  Cincinnati  area  was  long  ago  separated  by  Meek  as  a 
variety  of  the  ubiquitous  species  P.  sericea.  "  The  term  rugosa  was  given 
not  on  account  of  the  oblique  wrinkles  along  the  hinge-line,  but  on 
account  of  the  roughened  surface  of  the  general  exterior  surface  of  the 
valves,  especially  anteriorly.  This  roughened  surface  appears  due  to  the 
presence  of  numerous  very  thin  overlapping  films  of  shell  material.  These 
films  appear  to  consist  of  the  same  extremely  fine,  silky,  fibrous  material 
as  that  forming  the  compact  body  of  the  valves.  Sometimes  they  are 
traversed  by  the  same  radiating  striae  as  those  seen  on  that  part  of  the 
exterior  surface  of  the  valves  where  the  films  are  not  present.  The  films 
may  be  more  or  less  discrete  from  one  another,  but  in  some  specimens  they 
are  built  up  into  a  solid  mass,  resulting  in  a  thickening  of  the  valves 
exteriorly.  At  the  exterior  margin  of  the  pedicle  valve,  this  thickening 
may  reach  a  total  of  fully  2  mm.,  and  frequently  the  anterior,  more  or 
less  vertical  slope  of  this  thickening  is  crossed  by  lines  evidently  corre- 
sponding to  the  extensions  of  the  radiating  striae.  The  thickening 
usually  is  confined  to  the  anterior  half  or  third  of  the  valves.  It  may 
result  in  a  succession  of  concentric  bands,  the  one  nearest  the  anterior 
margin  being  the  most  conspicuous.  At  other  times,  the  thickening 
increases  evenly,  without  any  concentric  banding,  but,  most  frequently 
it  is  more  or  less  irregular,  the  films  being  more  or  less  warped  or  broken 
into  shreds." — Foerste,  1912. 

Occurrence. — MARTINSBURG  SHALE  (Eden  division).  Jordans  Knob, 
one  and  one-half  miles  northeast  of  Fort  Loudon,  Pennsylvania,  and  in  the 
same  horizon  on  Rickard  Mountain,  Maryland.  Eden  shale  of  the  Ohio 
Valley. 

Collections. — Maryland  Geological  Survey,  U.  S.  National  Museum. 

17 


256  SYSTEMATIC  PALEONTOLOGY 

Genus  CHRISTIANIA  Hall  and  Clarke 
CHRISTIANIA  TRENTONEXSIS  Euedemann 

Plate  XLVIII,  Figs.  16-18 

Christiania  trentonensis  Ruedemann,   1902,   Bull.   New   York   State  Mus., 
No.  49,  p.  21,  pi.  ii,  figs.  2-6. 

Description. — "  Shell  small,  convexo-concave,  somewhat  variable  in 
shape,  rotundo-quadrate  to  rotundo-rectangular ;  sides  sub-parallel  or 
slightly  converging  to  the  cardinal  line;  front  rounded.  Hinge  line 
straight,  only  slightly  shorter  than  the  greatest  width  of  the  valve  in  the 
middle  part;  cardinal  extremities  obtusely  angular,  having  the  appear- 
ance of  flattened  ears.  Pedicle  valve  uniformly  and  strongly  convex; 
umbo  slightly  projecting  and  very  narrow ;  beak  obscure.  Cardinal  area 
narrow  ( ?)  ;  interior  of  pedicle  valve  not  observed.  Brachial  valve 
strongly  concave,  beak  hardly  projecting  beyond  the  long,  straight  hinge 
line.  Cardinal  extremities  strongly  developed,  flat;  area  very  small, 
cardinal  process  small,  bipartite  on  its  anterior  face;  the  lobes  being 
denticulate  anteriorly  with  from  three  to  five  small  denticles  on  each 
side.  Crural  plates  very  long  and  slightly  divergent;  the  lower  portion 
produced  on  each  side  as  a  strongly  elevated  wall  with  perpendicular 
sides  extending  in  the  original  direction  of  the  crural  plates  close  to  the 
ante-lateral  angle,  where  it  recurves  and  returns,  parallel  to  the  median 
axis  and  nearly  in  a  straight  line  as  a  still  more  prominent  wall  merging 
into  the  base  of  the  cardinal  process.  The  elongate,  symmetric,  sub- 
rectangular  spaces  thus  formed  are  each  divided  transversely  by  a  vertical 
ridge  about  one-third  of  the  length  of  the  valve  from  the  cardinal  line. 
The  long  narrow  space  between  the  inner  muscular  walls  is  also  bounded 
anteriorly  by  a  low,  rounded,  curving  ridge  and  divided  in  the  median  line 
of  the  shell  by  a  low,  rounded,  longitudinal  ridge.  The  anterior  half  of 
the  surface  of  the  long  anterior  adductors  is  very  rugose  and  radially 
striated. 

"  The  surface  is  covered  with  concentric  lines  of  growth  and  radiating 
quite  widely  separated,  filiform  striae  with  smooth,  flat,  interspaces." — 
Ruedemann,  1902. 


MARYLAND  GEOLOGICAL  SURVEY  257 

Occurrence. — CHAMBERSBURG  LIMESTONE  (Christiania  bed).     Appa- 
lachian Valley  of  Pennsylvania.,  Maryland,  and  Virginia. 
Bysedorph  conglomerate  at  base  of  Trenton,  Xew  York. 
Collections. — Maryland  Geological  Survey,  U.  S.  National  Museum. 

CHRISTIANIA  LAMELLOSA  n.  sp. 
Plate  XLIX,  Figs.  3-10 

Description. — The  strongly  lamellose  surface  of  this  brachiopod  is 
sufficient  reason  for  discriminating  it  from  all  other  described  species  of 
the  genus.  The  general  outline  of  the  shell  is  not  unlike  several  small 
shells  of  the  Chambersburg  and  early  Trenton  rocks  referred  to  both 
Christiania  and  Plectambonites,  but  the  interior  of  the  valve  shows  the 
characteristic  markings  of  the  former  genus.  The  pedicle  valve  is  strongly 
convex  and  bears  the  concentric  lamellae  almost  to  the  beak.  The 
brachial  valve  is  as  strongly  concave,  with  a  smooth  surface.  The  average 
shell  is  9  mm.  high  and  about  10  mm.  wide. 

Occurrence. — MARTINSBURG  SHALE  (Sinuites  bed).  Southern  Penn- 
sylvania; also  abundant  at  the  same  horizon  in  northern  Virginia,  the 
types  being  from  Strasburg. 

Collections. — Maryland  Geological  Survey,  U.  S.  National  Museum. 

Genus  LEPTAENA   Dalman 

LEPTAENA  CHARLOTTAE  Winchell  and  Schuchert 
Plate  XLI,  Figs.  11-13 

Leptaena  cnarlottae  Winchell  and   Schuchert,  1892,  Amer.   Geol.,  vol.  ix, 

p.  288. 
Leptaena  charlottae  Winchell  and  Schuchert,  1893,  Geol.  Minnesota,  vol.  iii, 

p.  410,  pi.  xxxii,  figs.  1-5. 
Strophomena  halli  Sardeson,  1892,  Bull.  Minnesota  Acad.  Nat.  Sci.,  vol.  iii, 

p.  334,  pi.  iv,  figs.  36,  38. 

Description. — "  Shell  small,  transversely  semioval,  plano-convex,  ge- 
niculate,  with  the  sides  slightly  convex  and  converging  to  the  broadly 
rounded  front,  or  drawn  out  tongue  shaped;  hinge-line  as  long  as,  or 


258  SYSTEMATIC  PALEONTOLOGY 

somewhat  shorter  than,  the  greatest  width  of  the  shell.  Surface  marked 
by  fine,  closely  crowded,  alternating  striae,  as  in  Rafinesquina  alternata, 
crossed  by  exceedingly  delicate  concentric  lines  and  over  the  central  flat 
disc  of  each  valve  by  more  or  less  continuous  zigzag  undulations  or 
wrinkles. 

"  Ventral  valve  depressed-convex  over  the  greater  portion  of  the  shell 
and  more  or  less  suddenly  bent  downward  or  geniculated  along  the 
margin,  especially  anteriorly.  Cardinal  area  wide,  broadly  triangular, 
with  a  convex  deltidium,  wider  than  long,  apically  perforated  by  a  rather 
large  pedicle  opening,  posteriorly  excavated  and  completely  occupied  by 
the  chilidium  of  the  other  valve.  Crenulated  hinge  teeth  prominent  and 
supported  by  short  dental  plates,  which  are  attached  to  the  elevated  outer 
margin  of  the  small,  transversely  oval  muscular  area.  Within  this  area, 
in  the  center  of  the  mesial  thickening,  are  placed  the  short  and  narrow 
adductors,  surrounded  by  the  large  diductors,  and  outside  these,  at  the 
base  of  the  dental  plates,  are  the  distinct  scars  of  the  small  adjusters. 
Surface  marked  by  delicate,  crowded  papillae,  strongest  in  front  of  the 
muscular  area,  and  in  the  thin  shells  by  the  wrinkling  of  the  outer  surface. 

"  Dorsal  valve  nearly  flat,  with  the  anterior  margin  more  or  less 
reflexed  downward.  Cardinal  area  narrow,  about  one-third  that  of  the 
other  valve,  with  a  broad  and  strongly  convex  chilidium.  Dental  sockets 
deep;  crural  plates  slender,  very  bilobed,  cordate  cardinal  process;  in 
front  of  this  is  a  short,  low  septum  separating  the  inconspicuous  septa. 
Just  inside  the  outer  margin  of  the  valve  is  situated  a  prominent,  rounded 
ridge  of  the  same  nature  as  that  in  L.  rhomboidalis." — "Winchell  and 
Schuchert,  1893. 

Leptaena  charlottae  differs  conspicuously  from  all  other  American 
species  of  the  genus  in  its  zigzag,  concentric  surface  corrugations. 

Occurrence. — CHAMBERSBURG  LIMESTONE  ( Caryocystites  bed).  Fort 
Loudon  and  Blue  Spring,  Franklin  County,  Pennsylvania. 

The  type  specimens  were  described  from  the  Decorah  shales  division  of 
the  Black  River  at  Minneapolis  and  St.  Paul,  Minnesota. 

Collections. — Maryland  Geological  Survey,  TJ.  S.  National  Museum. 


MARYLAND  GEOLOGICAL  SURVEY  259 

LEPTAENA  GIBBOSA  (James) 
Plate  LIV,  Fig.  25 

Strophomena  gibbosa  James,  1874,  Cincinnati  Quart.  Jour.  Sci.,  vol.  i,  p.  333. 
Leptaena  gibbosa  Foerste,  1909,  Bull.   Sci.  Lab.  Denison  Univ.,  vol.  xiv, 

p.  316. 
Leptaena  gibbosa  Foerste,  1912,  Idem.,  vol.  xvii,  p.  116,  pi.  i,  figs.  5a-c. 

Description. — "  Shell  fragile,  semi-oval ;  cardinal  line  extended  to  or 
a  little  beyond  the  width  of  the  shell  farther  forward,  deflected  at  the 
extremities ;  lateral  and  front  margins  regularly  rounded.  Ventral  valve 
slightly  convex  in  the  umbonal  region,  hut  at  about  one-third  or  one-half 
the  distance  from  the  beak,  toward  the  front  and  lateral  margins,  it 
curves  suddenly  upward,  then  rounds  off,  and  is  deflected  as  suddenly  the 
other  way  to  the  front  and  sides,  forming  a  high  rounded  ridge,  giving 
to  the  shell  a  decidedly  gibbous  form ;  this  hump  extends  to  about  l/8th 
of  an  inch  of  the  cardinal  line  on  each  side,  where  the  shell  is  rather 
depressed  from  the  umbonal  slopes  outwards  to  the  deflected  extremities 
immediately  in  front  of  the  cardinal  line;  cardinal  area  linear;  beak 
rather  prominent,  projecting,  minutely  perforated;  six  to  eight  slight 
wrinkles  on  the  umbonal  region.  Surface  covered  by  fine  radiating  striae, 
increased  by  interstitial  additions,  somewhat  variable  in  size  on  the  front 
slope,  but  quite  uniform  on  the  umbone  and  to  the  lateral  margins; 
crossed  by  fine  concentric  striae.  Interior  not  observed. 

"  Dorsal  valve  (exterior)  gently  concave  to  about  the  middle,  where  it 
makes  a  sudden  curve,  conforming  to  the  shape  of  the  other  valve;  the 
two  valves  are  so  closely  drawn  together  as  to  leave  scarcely  any  visceral 
space;  beak  very  little  elevated  above  the  cardinal  line;  area  no  more 
than  a  rather  sharp  edge  of  the  hinge ;  radiating  striae,  as  far  as  observed 
same  as  on  the  ventral  valve.  Interior  nearly  flat,  or  slightly  convex  to 
the  base  of  the  ridge,  in  front  and  laterally  to  within  about  one-quarter 
or  one-eighth  of  an  inch  of  the  cardinal  line,  where  there  is  a  flat  depres- 
sion extending  to  the  lateral  margins ;  the  curve  to  the  front  from  the  top 
of  this  ridge  is  abrupt,  corresponding  to  the  exterior;  cardinal  process 
bifid,  erect,  rather  prominent,  curving  slightly  anteriorly,  crenulated 


2GO 

posteriorly  and  sloping  in  the  same  direction ;  sockei  ridges  short,  crenu- 
lated,  oblique;  rounded,  low,  wavy  elevations  just  bejrond  the  points  and 
in  front  of  the  socket  ridges ;  a  small  but  rather  deep  pit  immediately  in 
front  of  the  cardinal  process,  from  which  extends  a  low  mesial  ridge  to 
about  the  middle  of  the  shell  forwards,  where  it  fades  out ;  the  concentric 
wrinkles  of  the  exterior  show  through  slightly,  and  the  radiating  striae 
plainly,  with  small,  but  distinct,  radiating  rows  of  papillae,  which  are 
rather  distant  from  each  other,  to  the  ridge,  but  crowded  together  on  the 
front  slope  and  toward  the  lateral  margins ;  no  muscular  scars  observed, 

"  Width  of  a  specimen  of  medium  size,  measuring  from  the  points  of 
the  hinge-line,  1£  inches ;  length  about  three-fourths  of  an  inch." — James, 
1874. 

Occurrence. — MARTINSBURG  SHALE  (Eden  division).  Jordans  Knob, 
one  and  one-half  miles  northeast  of  Fort  Loudon,  Pennsylvania.  Eden 
shale  of  the  Ohio  Valley. 

Collections. — Maryland  Geological  Survey,  U.  S.  National  Museum. 

LEPTAENA  TENUISTRIATA  Sowerby  var. 
Plate  XLIX,  Fig.  2 

Leptaena  tenuistriata   Sowerby,   1839,   in   Murchison's    Sil.    Syst,   vol.   ii, 

p.  636,  pi.  xxii,  fig.  2a. 
Leptaena  tenuistriata  Foerste,  1910,  Bull.  Sci.  Lab.  Denison  Univ.,  vol.  xvi, 

p.  45,  pi.  v,  fig.  9. 

Description. — The  particular  ^forrn  of  Leptaena  found  in  the  Sinuites 
bed  of  southern  Pennsylvania  is  in  general  aspect  quite  like  specimens 
from  a  similar  lower  Trenton  horizon  in  Tennessee  identified  by  Foerste 
as  L.  tenuistriata  Sowerby.  Direct  comparison  with  typical  British 
specimens  is  necessary  before  the  identity  of  the  American  form  can  be 
determined  with  certainty.  In  the  meantime  it  is  believed  best  to  record 
the  Sinuites  zone  species  as  a  variety. 

Occurrence. — MARTINSBURG  SHALE  (Sinuites  bed).  One  mile  south 
of  St.  Thomas  and  other  localities  in  southern  Pennsylvania. 

Collection. — U.  S.  National  Museum. 


MARYLAND  GEOLOGICAL  SURVEY  261 

Genus  RAFINESQUINA  Hall  and  Clarke 

RAFINESQUINA  CHAMPLAINENSIS  Raymond 

Plate  XLI,  Figs.  8,  9 

Rafinesquina  champlainehsis  Raymond,  1902,  Bull.  Amer.  Pal.,  vol.  iii,  p.  37, 

pi.  xviii,  figs.  5,  6. 
Rafinesquina  champlainensis  Raymond,  1911,  Ann.  Carnegie  Mus.,  vol.  vii, 

p.  233,  figs.  6-9. 

Description. — "  Shell  large,  ventricose,  almost  hemispheric.  Length 
and  width  nearly  equal.  Hinge  line  usually  a  little  longer  than  the  width 
below,  and  the  cardinal  extremities  are  produced  into  broad,  rounded 
ears.  The  pedicle  valve  is  strongly  and  evenly  convex,  the  highest  point 
being  about  the  middle  of  the  valve.  The  brachial  valve  is  flat  on  the 
umbo  and  concave  in  front,  following  the  curvature  of  the  opposite 
valve.  Cardinal  area  on  the  pedicle  valve  rather  wide. .  Delthyrium 
covered  by  a  broad  convex  deltidium.  Area  of  brachial  valve  linear. 
The  surface  is  marked  by  very  numerous  fine  radiating  striae,  every 
third  or  fourth  one  of  which  is  stronger  than  the  ones  between.  The 
striae  increase  by  implantation.  In  the  partially  exfoliated  state  in 
which  the  specimens  are  usually  found,  the  striae  appear  nearly  equal 
and  the  shell  structure  fibrous." — Raymond,  1902. 

Occurrence. — CHAMBERSBURG  LIMESTONE  ( Caryocystites  bed).  Fort 
Loudon  and  Blue  Spring,  Franklin  County,  Pennsylvania. 

In  the  type  localities  in  the  Lake  Champlain  area,  this  species  occurs 
in  the  Middle  Chazy  (Crown  Point)  limestone.  It  has  been  identified 
in  the  stratigraphically  equivalent  Lenoir  limestone  of  east  Tennessee 
and  Virginia. 

Collection. — U.  S.  National  Museum. 

RAFINESQUINA  MINNESOTENSIS  (Winchell) 
Plate  XLV,  Fig.  4 

Strophomena  deltoidea  Owen  (not  Conrad),  1844,  Geol.  Expl.  Iowa,  Wis- 
consin and  Illinois,  pi.  xvi,  fig.  8;  pi.  xvii,  fig.  6. 

Strophomena  minnesotensis  N.  H.  Winchell,  1881,  Ninth  Ann.  Rept.  Geol. 
Nat.  Hist.  Surv.  Minnesota,  p.  120. 


262  SYSTEMATIC  PALEONTOLOGY 

Rafinesquina  minnesotensis  Hall  and  Clarke,  1892,  Pal.  New  York,  vol.  viii, 

pt.  1,  pi.  31,  figs.  25-29. 
Rafinesquina  minnesotensis  Winchell  and  Schuchert,  1893,  Geol.  Minnesota, 

vol.  iii,  p.  401,  pi.  xxxi,  figs.  25-29. 

Description. — •"  Shell  semi-oblong  or  semi-oval,  with  the  cardinal  angle 
about  90,  or  less  than  90;  diameter  from  six  to  nine  lines  transversely, 
and  from  four  and  a  half  to  eight  lines  perpendicularly ;  the  ventral  valve 
convex,  sometimes  more  suddenly  deflected  after  passing  the  visceral 
area;  dorsal  valve  gently  concave,  but  reflexed  more  rapidly  about  the 
margin ;  the  exterior  of  the  convex,  ventral  valve  marked  by  fine,  radiating 
striae,  every  third,  fourth  or  fifth  one  being  larger  than  the  intervening 
ones;  interior  of  the  convex  (ventral)  valve,  which  is  best  known  from 
its  frequent  casts,  shows  a  large  muscular  impression  somewhat  bilobate 
in  front  and  larger  in  proportion  to  the  size  of  the  valve ;  scars  of  adduc- 
tor muscles  closely  approximate,  small  and  in  many  casts  of  this  valve 
undistinguishable ;  behind  they  are  separated  (on  the  casts)  by  a  short 
mesial  ridge,  which  between  them  becomes  a  narrow  mesial  furrow  and 
then  a  deep  furrow,  terminating  at  the  sinus  between  the  outer  larger 
scars;  the  outer  larger  scars  (diductors)  are  radiately  striated  from  the 
beak  (at  the  base  of  the  dental  lamellae  small  adjusters  are  occasionally 
indicated) ;  their  margins  are  strongly  marked  (on  the  cast)  along  their 
posterior  sides  by  distinct  grooves  formed  by  the  dental  plates,  which 
diverge  at  once  from  the  foramen  at  an  angle  of  100-1200,  running  nearly 
straight  to  the  outer  margins  of  the  muscular  scar,  when  they  curve 
slightly  towards  the  front ;  the  anterior  and  lateral  margins  of  the  general 
muscular  impression  are  slightly  marked  on  the  casts;  outside  of  the 
muscular  scar  is  a  shallow  marginal  impressed  line  which  is  most  evident 
at  the  cardinal  angles  as  it  converges  toward  the  beak ;  the  interior  edge 
of  the  cardinal  line  is  carinate  from  the  teeth  to  the  cardinal  angles ;  the 
details  of  the  markings  in  the  apex  of  the  beak  are  seen  on  the  valve  itself 
to  consist  of  two  short,  distinct,  diverging  ridges  extending  not  much 
beyond  the  hinge  teeth  (enclosing  the  adductor  scars),  between  the 
anterior  ends  of  which  rises  a  short  mesial  ridge  of  about  the  same  size 
and  length,  with  faint  linear  ridges  parallel  with  it  on  each  side,  which 


MARYLAND  GEOLOGICAL  SURVEY  263 

extend  a  little  further  forward  than  the  mesial  ridge.  The  mesial  ridge 
first  gives  place  to  a  flat,  unmarked  interval,  when  it  again  rises  more 
conspicuously,  but  narrower  and  sharper,  extending  nearly  to  the  sinus 
separating  the  lobes  of  the  outer  muscular  scar.  The  cardinal  area  of  tho 
convex  valve  slopes  from  the  hinge-line  obliquely  backward,  instead  01 
being  in  plane  with  the  lateral  edges,  thus  differing -from  R.  alternata. 
From  three  to  five  undulations  of  the  shell  transverse  to  the  cardinal  line 
are  seen  often  between  the  umbo  and  the  cardinal  angles,  the  heavier  ones 
being  near  the  cardinal  angles.  The  cardinal  process  is  bifid  and  promi- 
nent, the  two  parts  being  short,  smooth,  dentate  protruberances  that 
stand  prominently  exposed  about  parallel  with  the  plane  of  the  cardinal 
area. 

"  The  interior  of  the  dorsal  valve  is  very  different  from  that  of  the 
dorsal  valve  of  R.  alternata.  The  general  visceral  disc  is  nearly  flat,  sur- 
rounded by  a  suddenly  flexed  margin,  inside  of  which  is  a  shallow  im- 
pressed broad  line,  most  evident  round  the  front;  inside  the  cardinal 
angles  are  a  few  scattered,  radiately  interrupted,  short  ridges  or  elevations 
(genital  markings),  but  these  do  not  prevail  along  the  side  nor  in  front, 
the  surface  there  being  smooth  or  finely  granulated  instead ;  in  the  center 
of  the  valve  are  five  smooth,  abrupt,  digitately  spreading  ridges,  the 
middle  one  of  which  is  a  little  larger  and  longer  than  the  others ;  these 
rise  more  abruptly  at  their  anterior  extremities  than  behind,  but  none 
of  them  reach  the  beak,  or  even  the  umbonal  region,  though  the  exterior 
pair  of  lateral  ones  are  placed  further  back  than  the  others,  converging 
at  an  angle  of  about  700  (and  often  pass  through  the  large  pair  of  adductor 
scars).  Socket  (crural)  ridges  very  short  and  widely  divergent;  behind 
them  are  small,  doubly  grooved  sockets.  The  beak  of  the  ventral  valve  is 
often  perforated  by  a  minute,  circular,  pedicle  opening."— Winchell  and 
Schuchert,  1893. 

Occurrence. — CHAMBERSBURG  LIMESTONE  (Echinospherites  bed).  Wil- 
son and  Pinesburg  Station,  Maryland.  A  characteristic  Black  River 
species  of  the  Mississippi  Valley. 

Collections. — Maryland  Geological  Survey,  TJ.  S.  National  Museum. 


264  SYSTEMATIC  PALEONTOLOGY 

BAFINESQUINA  MINNESOTENSIS  INQUASSA  (Sardeson) 
Plate  XLV,  Figs.  5,  6 

Strophomena  inquassa   Sardeson,   1892,   Bull.   Minnesota   Acad.   Nat.   Sci., 

vol.  iii,  p.  334,  pi.  v,  figs.  22-24. 
Rafinesquina  minnesotensis  var.  inquassa  Winchell  and  Schuchert,  1893, 

Geol.  Minnesota,  vol.  iii,  p.  403,  pi.  xxxi,  figs.  27,  28. 

Description. — The  brachiopod  to  which  this  varietal  name  has  been 
applied  differs  from  R.  minnesotensis  in  its  larger  and  more  convex  shell 
with  a  wide  ventral  hinge  area.  Externally  this  shell  also  has  a  consider- 
able resemblance  to  R.  alternata.,  but  the  interiors  of  each  exhibit  con- 
siderable difference,  the  two  ridges  on  each  side  of  the  median  septum  in 
the  present  variety  being  reduced  to  one  in  R.  alternata. 

Occurrence. — CHAMBEESBUEG  LIMESTONE  (Echinospherites  bed). 
Southern  Pennsylvania  and  at  Pinesburg  Station  and  Wilson,  Maryland. 

Collections. — Maryland  Geological  Survey,  U.  S.  National  Museum. 

RAFIXESQUIXA  SQUAMULA  (James) 
h  Plate  LIV,  Figs.  3-4;  Plate  LVIII,  Fig.  4 

Strophomena  squamula  James,  1874,  Cincinnati  Quart.  Jour.  Sci.,  vol.  i, 

p.  335. 
Raflnesquina  squamula  Foerste,  1914,  Bull.  Sci.  Lab.  Denison  Univ.,  vol.  xvii, 

p.  264. 

Description. — "  Shell  small,  thin,  semi-oval  in  outline,  broader  than 
long ;  hinge-line  varying  from  a  little  more  to  a  little  less  than  the  greatest 
breadth  of  the  shell  farther  forward. 

"  Dorsal  valve  slightly  convex  or  nearly  flat ;  cardinal  line  straight ; 
cardinal  area  linear ;  a  slight  'depression  immediately  forward  of  the  beak. 
Surface  covered  with  fine,  rounded  radiating  striae  of  nearly  uniform 
size,  increased  toward  the  free  margin  by  bifurcation. 

"Ventral  valve  slightly  convex;  beak  and  hinge-line  slightly  project- 
ing; cardinal  area  narrow,  a  little  the  widest  in  the  middle;  foramen 
triangular  and  nearly  closed  by  the  cardinal  process  of  the  other  valve; 
a  strong  mesial  rib  extending  from  beak  to  the  front ;  surface  covered  by 
fine,  rounded,  radiating  striae,  which  bifurcate  once  or  twice  before 


MARYLAND  GEOLOGICAL  SURVEY  265 

reaching  the  free  margins ;  the  striae  starting  at  and  near  the  beak  more 
prominent  than  the  branching  ones ;  crossed  by  very  fine  concentric  lines, 
visible  only  under  a  good  magnifier,  and  even  then  in  some  cases  quite 
obscure.  Visceral  space  very  little,  the  valves  being  so  closely  drawn 
together,  translucent.  Interior  not  observed.  Breadth  of  a  full-sized 
specimen,  5/8  inch;  length,  1.2  inch." — Foerste,  1914. 

Although  hitherto  unfigured  the  species  has  long  been  known  as  an 
interesting  shell  of  the  Cincinnati  area  where  it  occurs  at  several  horizons 
in  the  Eden  shale  and  in  the  Fairview  formation  of  the  Maysville  group. 
The  above  description  was  based  upon  the  type  specimens  and  the  ex- 
amples illustrated  were  identified  by  the  author  of  the  species. 

Occurrence. — MARTTNSBURG .SHALE  (Eden  division).  Jordans  Knob, 
one  and  one-half  miles  northeast  of  Fort  London,  Pennsylvania,  and  in 
sandstone  fragments  on  Eidkard  Mountain,  Washington  County, 
Maryland. 

The  Orthorhynchula  bed  at  the  top  of  the  Fairview  division  of  the 
Martinsburg  shale,  just  under  the  Oswego  sandstone,  one  and  one-half 
miles  southeast  of  McConnellsburg  Pennsylvania,  has  furnished  numerous 
specimens. 

Collections. — Maryland  Geological  Survey,  TJ.  S.  National  Museum. 

KAFINESQUINA  ALTERNATA  (Emmons) 

Plate  LVII,  Fig.  8 

Strophomena  alternata  Emmons,   1842,   Geol.  New  York,   Kept.   2d   Dist., 

p.  395,  fig.  3. 
Leptaena  alternata  Hall,  1847,  Pal.  New  York,  vol.  i,  pp.  102,  286,  pi.  xxxi, 

fig.  1;  pi.  xxxi  A,  fig.  1;  pi.  Ixxix,  fig.  2. 
Raftnesquina  alternata  Hall  and  Clarke,  1892,  Pal.  New  York,  vol.  viii,  pt.  1, 

p.  282,  pi.  viii,  figs.  6-11,  27,  28;  pt.  2,  1895,  pi.  Ixxxiv,  figs.  17,  18. 

Description. — "  Broadly  semioval ;  length  and  breadth  about  as  12  to 
15;  hinge  line,  in  perfect  specimens,  a  little  longer  than  the  width  of  the 
shell,  slightly  reflected  at  the  extremities,  which  sometimes  become  short, 
acute  ears ;  cardinal  area  narrow,  the  callosity  of  the  ventral  valve  nearly 


266  SYSTEMATIC  PALEONTOLOGY 

filling  the  triangular  foramen  of  the  dorsal  valve;  beak  uniformly  per- 
forated with  a  minute  circular  opening;  dorsal  valve  depressed  convex, 
sometimes  more  convex  in  the  middle,  suddenly  deflected  near  the  margin 
and  flattened  towards  the  cardinal  line ;  ventral  valve  concave,  gradually 
or  sometimes  suddenly  inflected  towards  the  basal  margin ;  surface  marked 
by  fine  rounded  radiating  striae,  which  alternate  at  unequal  intervals 
with  coarser  ones;  striae  increasing  in  number  towards  the  margin  of 
the  shell,  crossed  by  fine  elevated  concentric  lines  and  a  few  imbricating 
lines  of  growth."— Hall,  1847. 

This  very  abundant  brachiopod  has  such  a  long  range  that  it  is  of  little 
value  for  detailed  stratigraphic  purposes,  although  it  is  true  that  the 
varieties  or  mutations  of  the  species  which  occur  at  various  horizons  hold 
their  characters  fairly  well  if  minute  discriminations  are  made.  The 
illustrations  represent  the  common  Maysville  form  of  the  species  occur- 
ring in  the  Pulaski  shale  of  New  York.  The  same  form  occurs  at  the 
corresponding  horizon  in  Pennsylvania  and  Maryland. 

Occurrence. — MARTINSBURG  SHALE  (Fairview  division).  Tuscarora 
Mountain,  one  and  one-half  miles  southwest  of  McConnellsburg,  Penn- 
sylvania. 

Collections. — Maryland  Geological  Survey,  IT.  S.  National  Museum. 

Genus  TRIPLECIA  Hall 

TRIPLECIA  (CLIFTONIA)  SIMULATRIX  n.  sp. 
Plate  XLIX,  Figs.  11-13 

Description. — The  strata  of  the  Chambersburg  limestone  succeeding 
the  Lowville  division  and  the  Sinuites  bed  at  the  base  of  the  Martinsburg 
shale,  contain  a  radially  plicated  brachiopod  which  is  so  similar  to  small 
examples  of  Platystrophia  that  its  references  to  that  genus  would  seem 
proper.  However,  upon  close  examination  this  new  species  is  found  to 
have  the  characteristic  bifurcated  cardinal  process  of  Triplecia  and  to 
lack  the  surface  granulations  of  Platystrophia.  The  open  delthyrium  of 
Platystrophia  is  also  absent,  but  the  deltidium  of  the  Strophomenidae 
is  present. 


MARYLAND  GEOLOGICAL  SURVEY  267 

This  species  belongs  to  the  genus  or  subgemis  Cliftonia  established  by 
Foerste  for  the  plicated  forms  of  Triplecia,  which  was  well  described  as 
Oxoplecia  by  Miss  Alice  Wilson.  Triplecia  (Cliftonia)  simulatrix  is 
related  to  Oxoplecia  calhouni  Wilson,  from  the  base  of  the  Collingwood 
(Trenton)  shale  of  Ottawa,  Canada,  but  differs  in  its  coarser  plication, 
this  feature  being  most  marked  on  the  sides  of  the  shell. 

Occurrence. — MABTINSBURG  SHALE  (Sinuites  bed).  One  mile  south 
of  St.  Thomas,  Pennsylvania,  and  at  Strasburg,  Virginia.  The  species 
occurs  also  in  the  Echinospherites,  Nidulites,  and  Christiania  beds  of  the 
Chambersburg  limestone  in  Pennsylvania,  Maryland,  and  Virginia. 

Collections. — Maryland  Geological  Survey,  U.  S.  National  Museum. 

Superfamily  PENTAMERACEA 

Family  SYNTROPHIIDAE 

Genus  SYNTROPHIA  Hall  and  Clarke 

SYNTROPHIA  LATERALIS  (Whitfield) 

Plate  XXXIII,  Figs.  4,  5 

Triplesia  lateralis  Whitfield,   1886,  Bull.   Amer.   Mus.  Nat.   Hist.,   p.   303, 

pi.  xxiv,  figs.  9-11. 
Syntrophia  lateralis  Hall  and  Clarke,  1892,  Pal.  New  York,  vol.  viii,  pt.  1, 

p.  270;  ibid.,  vol.  viii,  pt.  2,  p.  216,  pi.  Ixii,  figs.  1-10. 
Syntrophia  lateralis  Weller,  1903,  Geol.  Surv.  New  Jersey,  Pal.,  vol.  ill, 

p.  126,  pi.  iv,  figs.  14,  15. 
Syntrophia  lateralis  Walcott,  1912,  Mon.  U.  S.  Geol.  Surv.,  vol.  li,  p.  802, 

text  fig.  11,  p.  299;  pi.  cii,  figs.  6,  6a-g. 

Description. — Shell  averaging  7.5  mm.  in  length  and  11  mm.  wide, 
subelliptical,  with  the  hinge-line  about  two-thirds  the  greatest  width  and 
the  cardinal  extremities  rounded.  Pedicle  valve  somewhat  convex,  promi- 
nent on  the  umbo,  but  a  little  flattened  near  the  cardinal  angles;  beak 
slightly  incurved  and  rather  blunt,  projecting  beyond  the  cardinal  mar- 
gin; mesial  sinus  broad,  shallow,  and  ill-defined,  not  extending  to  the 
beak.  Surface  with  fine,  concentric  lines  of  growth. 

Occurrence. — BEEKMANTOWN  LIMESTONE  (Cryptozoon  steeli  zone). 
At  various  localities  around  Williamsport  and  Hagerstown,  Maryland. 

Collections. — Maryland  Geological  Survey,  U.  S.  National  Museum. 


268  SYSTEMATIC  PALEOXTOLOGY 

Family  CLITAMBONITIDAE 

Genus  SGENIDIUM  Hall 

SCENIDIUM  ANTHONENSE  Sardeson 

Plate  XLVII,  Figs.  1-3 

Scenidium  anthonensis   Sardeson,   1892,  Bull.  Minnesota  Acad.  Nat.   Sci., 

vol.  iii,  p.  333,  pi.  iv,  fig.  7. 
Scenidium  halli  Hall  and  Clarke,  1892,  Pal.  New  York,  vol.  viii,  pt.  1,  p.  242, 

pi.  viiA,  figs.  33-39. 
Scenidium   anthonensis   Winchell   and    Schuchert,   1893,   Geol.   Minnesota, 

vol.  iii,  p.  381,  pi.  xxx,  figs.  20-23. 
Scenidium   anthonensis  Weller,    1903,   Geol.   Surv.   New  Jersey,   Pal.,  iii, 

p.  157,  pi.  x,  figs.  5-7. 

Description. — "  Shell  small,  subsemi-circular  in  outline,  the  greatest 
width  along  the  hinge-line.  Each  valve  marked  by  from  20  to  26  simple, 
rounded  plications.  Pedicle  valve  subpyramidal,  the  beak  erect;  cardinal 
area  large,  flat,  broadly  triangular,  with  a  large  delthyrium.  Along  the 
median  line  a  slight  elevation  or  ill-defined  fold  is  developed.  In  the 
interior  of  the  apical  portion  of  the  valve  is  a  small  spondylium.  Brachial 
valve  depressed,  convex,  with  a  slight  mesial  sinus.  The  dimensions  of 
an  average  specimen  arc :  Length,  2.5  mm.,  and  breadth,  5  mm." — 
Weller,  1903. 

Occurrence. — CHAMBEKSBURG  LIMESTONE  (Nidulites  bed).  Wilson 
and  Pinesburg  Station,  Maryland. 

Black  Eiver  group  of  Minnesota,  Iowa  and  New  Jersey. 

Collections. — Maryland  Geological  Survey,  U.  S.  National  Museum. 

SCENIDIUM  ?  MEROPE  (Billings) 
Plate  L,  Figs.  14-16 

Orthis  merope  Billings,  1865,  Geol.  Surv.  Canada,  Pal.  Fossils,  vol.  i,  p.  139, 

fig.  116. 
Scenidium  ?  merope  Hall  and  Clarke,  ?  1892,  Pal.  New  York,  vol.  viii,  pt.  1, 

p.  242,  pi.  viiA,  figs.  31,  32. 

Description,. — Shell  small,  subpyramidal,  somewhat  semi-circular,  with 
a  width  to  the  hinge-line  of  6  mm.  and  a  length  of  3  mm. ;  cardinal  angles 
acute,  from  60°  to  70° ;  exterior  surface  marked  with  25  to  30  strong 


MARYLAND  GEOLOGICAL  SURVEY  269 

radiating  striae.  Ventral  valve  elevated,  subpyramidal,  most  elevated 
at  the  beak,  thence  sloping  nearly  uniformly  to  the  sides  and  margin; 
area  large,  triangular,  at  right  angles  to  the  plane  of  the  margin ;  foramen 
large,  extending  to  the  beak.  Dorsal  valve  nearly  flat,  with  an  obscure 
mesial  sinus. 

This  interesting  little  brachiopod  is  somewhat  similar  to  several  small 
striated  forms,  and  a  restudy  of  the  types  is  necessary  before  its  true 
generic  characters  can  be  determined.  The  shell  from  Cincinnati,  Ohio, 
figured  by  Hall  and  Clarke  in  1892,  is  very  probably  of  a  distinct  species. 

Occurrence. — MARTINSBURG  SHALE  (Sinuites  bed).  Chambersburg, 
Pennsylvania.  Trenton  limestone  at  Ottawa,  Canada. 

Collection. — U.  S.  National  Museum. 

Family  PORAMBONITIDAE 

Genus  PARASTROPHIA  Hall  and  Clarke 

PARASTROPHIA  HEMIPLICATA  Hall 

Plate  XLVIII,  Figs.  8-11 

Atrypa  hemiplicata  Hall,  1847,  Pal.  New  York,  vol.  i,  p.  144,  pi.  xxxiii,  fig.  x. 
Anastrophia  ?  hemiplicata  Winchell  and  Schuchert,  1893,  Geol.  Minnesota, 

vol.  iii,  p.  382,  pi.  xxx,  fig.  29-31. 
ParastropMa  hemiplicata  Hall  and  Clarke,  1893,  Pal.  New  York,  vol.  viii, 

pt.  2,  p.  221,  pi.  Ixiii,  figs.  1-3. 
ParastropMa  hemiplicata  Weller,  1903,  Geol.  Surv.  New  Jersey,  Pal.,  vol.  iii, 

p.  158,  pi.  x,  figs.  11-14. 
ParastropMa  hemiplicata  Wilson,  1914,  Canada  Geol.  Surv.  Mus.  Bull.  No.  2, 

pp.  1-10,  pi.  iv,  figs.  1-34. 

Description. — "  Shell  subglobose,  subpentagonal  in  outline,  wider  than 
long,  the  thickness  frequently  equal  to  the  length.  Cardinal  line  short, 
with  sometimes  the  appearance  of  a  small  area  on  the  pedicle  valve.  Each 
valve  marked  by  from  8  to  12  simple,  subangular,  radiating  plications, 
which  reach  from  one-third  to  one-half  the  distance  from  the  margin 
to  the  beak,  leaving  the  older  portion  of  each  valve  smooth.  Besides  the 
radiating  plications,  the  entire  surface  is  marked  by  fine,  concentric,  sub- 
imbricating  lines  of  growth,  which  are  more  conspicuous  near  the  margin 


270  SYSTEMATIC  PALEONTOLOGY 

of  the  shell.  Pedicle  valve  depressed-convex,  with  an  abrupt,  broad,  but 
not  deep  sinus,  which  originates  about  one-third  of  the  distance  from  the 
beak  to  the  anterior  margin  and  is  produced  as  a  lingual  extension  in 
front  at  nearly  a  right  angle  to  the  plane  of  the  valve;  it  is  marked  by 
from  three  to  five  radiating  plications.  The  beak  is  small,  closely  in- 
curved; delthyrium  small  and  triangular.  Brachial  valve  strongly  con- 
vex or  gibbous,  with  a  broad  mesial  fold  commencing  one-third  of  the 
distance  from  the  beak  to  the  anterior  margin,  which  is  marked  by  from 
four  to  six  radiating  plications. 

"  The  dimensions  of  a  perfect  individual  are :  Length,  13  mm. ;  width, 
16.5  mm.;  thickness,  12.5  mm." — Weller,  1903. 

Occurrence. — CHAMBERSBURG  LIMESTONE  (Christiania  bed).  South- 
ern Pennsylvania.  Trenton  limestone  of  New  York,  New  Jersey,  etc. 

Collections. — Maryland  Geological  Survey,  U.  S.  National  Museum. 

order  TELOTREMATA 

Superfamily  RHYNCHONELLACEA 

Family  RHYNCHONELLIDAE 

Genus  CAMAROTOEGHIA    Hall  and  Clarke 

CAMAROTOECHIA  PLENA  (Hall) 

Plate  XLI,  Figs.  14-16 

Atrypa  plena  Hall,  1847,  Pal.  New  York,  vol.  i,  p.  21,  pi.  iv,  figs.  7. 
Gamarotoechia  plena  Raymond,  1911,  Ann.  Carnegie  Mus.,  vol.  vii,  p.  221, 
pi.  xxxiii,  figs.  7-18. 

Description. — "  The  adult  shells  are  subtriangular  to  subcircular  in 
outline,  with  a  wide,  shallow  ventral  sinus  and  a  somewhat  elevated  dorsal 
fold.  Surface  marked  by  from  17  to  24  strong  plications,  four  to  seven 
of  which  are  in  the  sinus  and  five  to  eight  on  the  fold.  The  plications 
are  crossed  by  zigzag  lines  of  growth,  which  are  sometimes  stronger  and 
sometimes  weaker  on  partially  exfoliated  specimens  than  of  specimens 
with  perfect  shells.  The  dorsal  beak  is  strongly  incurved,  and  the  umbo 
bears  a  slight  median  depression.  The  beak  of  the  pedicle  valve  is  only 


MARYLAND  GEOLOGICAL  SURVEY  271 

slightly  incurved,  and  does  not  rest  against  the  brachial  valve.  The 
delthyrium  is  open  throughout  life.  None  of  the  specimens  in  the  collec- 
tion show  the  deltidial  plates. 

"  Casts  of  the  interior  of  the  brachial  valve  show  a  low  septum  which 
extends  about  one-third  the  length  of  the  shell.  This  septum  divides  at 
its  posterior  end  as  in  the  typical  species  of  Camarotoechia,  but  there 
is  no  cardinal  process  as  in  Rhynchotrema." — Baymond,  1911. 

One  of  the  most  abundant  and  characteristic  Upper  Chazyan  (Val- 
cour)  fossils  of  the  Lake  Champlain  region  in  New  York  and  in  Canada. 

Occurrence. — CHAMBERSBURG  LIMESTONE  (Caryocystites  bed).  In  the 
strip  of  outcrop  from  Fort  Loudon  to  Blue  Spring,  Franklin  County, 
Pennsylvania. 

Collections. — Maryland  Geological  Survey,  U.  S.  National  Museum. 

Genus  ORTHORHYNGHULA    Hall  and  Clarke 
ORTHORHYNCHULA  LINNEYI  (James) 

Plate  LVII,  Figs.  9-12 

Orthis  f  linneyi  James,  1881,  Paleontologist,  vol.  v,  p.  41. 
Orthorhynchula  linneyi  Hall  and  Clarke,  1893,  Pal.  New  York,  vol.  viii,  pt.  2, 
p.  181,  pi.  Ivi,  figs.  10-13,  19. 

Description, — "Shells  rhynchonelloid  in  contour;  hinge-line  short, 
straight,  extending  for  about  one-third  the  transverse  diameter  of  the 
valves.  A  true  cardinal  area  is  present  on  both  valves,  that  of  the  pedicle- 
valve  being  considerably  the  broader,  erect,  often  incurved.  Each  valve 
also  possesses  a  distinct  triangular  delthyrium,  that  of  the  pedicle-valve, 
according  to  the  evidence  at  hand,  never  being  in  any  degree  closed  by 
deltidial  plates.  External  surface  strongly  and  simply  plicated,  the 
median  fold  and  sinus  being  well  developed.  On  the  interior,  the  pedicle- 
valve  possesses  blunt  teeth  which  rest  upon  the  laterally  thickened  walls 
of  the  valve  and  are  not  supported  by  lamellae.  Between,  and  slightly 
in  front  of  these  lies  a  short,  subquadrate  muscular  scar.  The  brachial 
valve  possesses  a  linear  cardinal  process,  on  either  side  of  which  are  two 
discrete  crural  plates,  sharply  concave  on  the  upper  surface  and  diverging 

18 


272  SYSTEMATIC  PALEONTOLOGY 

anteriorly   for   a   considerable   distance.      Shell-substance   fibrous,    im- 
punetate."— Hall  and  Clarke,  1893. 

Although  occurring  at  two  distinct  geological  horizons  this  interesting 
brachiopod,  when  considered  with  the  associated  fossils,  is  highly  char- 
acteristic of  each  horizon.  The  species  is  so  well  developed  at  the  top  of 
the  Fairview  formation  of  the  Maysville  group  that  the  name  Ortho- 
rhynchula  bed  has  been  applied  to  these  strata.  In  this  bed  the  species 
often  grow  to  an  unusual  size,  some  examples  being  an  inch  or  more  in 
length. 

Occurrence. — MARTIXSBURG  SHALE   (Fairview  division).     Tuscarora 
Mountain,  one  and  one-half  miles  southeast  of  McConnellsburg,  Pennsyl- 
vania.   Upper  Trenton  of  Kentucky  and  Tennessee,  Lower  Maysville  of 
the  Ohio  Valley,  Virginia,  Maryland,  and  Pennsylvania. 
.  Collections. — Maryland  Geological  Survey,  IT.  S.  National  Museum. 

Genus  ZYGOSPIRA  Hall 

ZYGOSPIRA  RECURVIROSTRIS  (Hall) 

Plate  XLII,  Figs.  9-12 

Atrypa  recurvirostris  Hall,  1847,  Pal.  New  York,  vol.  i,  p.  140,  pi.  xxxiii, 

fig.  5. 
Zygospira  recurvirostris  Winchell  and   Schuchert,  1893,  Geol.   Minnesota, 

vol.  iii,  p.  466,  pi.  xxxiv,  figs.  38-41. 
Zygospira  recurvirostris  Hall  and  Clarke,  1895,  Pal.  New  York,  vol.  viii, 

pt.  2,  pi.  liv,  figs.  1-6. 
Zygospira  recurvirostris  Weller,  1903,  Geol.  Surv.  New  Jersey,  Pal.,  vol.  iii, 

p.  161,  pi.  x,  figs.  23-26. 

Description. — "  Shell  small,  subcircular  or  longitudinally  subovate  in 
outline,  subglobular;  surface  of  both  valves  marked  by  24  to  28  rounded 
or  subangular,  radiating  plications,  which  are  crossed  by  fine,  concentric 
lines  of  growth.  Pedicle  valve  gibbous,  with  its  greatest  elevation  near 
the  center,  subcarinate  near  the  beak,  the  keel  becoming  broader  toward 
the  front  and  forming  a  rather  well-defined,  more  or  less  flat-topped 
median  fold;  beak  small  and  pointed,  incurved  over  the  beak  of  the 
brachial  valve.  Brachial  valve  less  convex  than  the  other,  marked  by  a 


MARYLAND  GEOLOGICAL  SURVEY  273 

rather  broad,  shallow,  rounded  median  sinus,  which  corresponds  with  the 
fold  of  the  pedicle  valve  and  which  reaches  nearly  to  the  beak.  The 
dimensions  of  an  average  specimen  are :  Length,  6  mm. ;  width,  6  mm. ; 
thickness,  4  mm."— Weller,  1903. 

An  abundant  species  in  its  various  forms,  in  the  Black  River  and 
Trenton  rocks  of  New  York  and  Canada  and  the  Ohio  and  Mississippi 
valleys. 

Occurrence, — CHAMBERSBURG  LIMESTONE  (Tetradium  cellulosum 
bed).  Railroad  cut  two  miles  southwest  of  Marion  and  at  Fort  Loudon, 
Franklin  County,  Pennsylvania,  where  the  Lowville  form  occurs  in  some 
abundance. 

Collections. — Maryland  Geological  Survey,  U.  S.  National  Museum. 

ZYGOSPIRA  EXIGUA  (Hall) 

Plate  XLVIII,  Figs.  19,  20 

Atrypa  exigua  Hall,  1847,  Pal.  New  York,  vol.  i,  p.  141,  pi.  xxxiii,  fig.  6. 
Protozyga  exigua  Hall  and  Clarke,  1893,  Pal.  New  York,  vol.  viii,  pt.  2, 
p.  149,  figs.  137,  138,  pi.  liv,  figs.  47,  48. 

Description. — "  Plano-convex ;  length  and  breadth  about  equal ;  cardi- 
nal line  considerably  extended ;  dorsal  valve  elevated  in  a  ridge  along  the 
middle,  depressed  at  the  sides,  and  slightly  inflected  towards  the  cardinal 
extremities;  beak  small,  straight,  much  extended  beyond  the  cardinal 
line ;  ventral  valve  considerably  shorter  than  the  dorsal,  depressed-convex, 
with  a  broad  depression  along  the  center,  reaching  half  way  from  the  base 
to  the  beak;  beak  small,  and  close  pressed  into  the  foramen  beneath  the 
beak  of  the  opposite  valve;  surface  scarcely  marked  with  fine  concentric 
lines,  and  a  few  indistinct  longitudinal  rays  near  the  margin. 

"  In  the  largest  specimen  which  I  have  seen,  there  are  evidences,  under 
a  magnifier,  of  small  radii  commencing  below  the  center  of  the  valve. 
Since,  however,  they  are  not  perceptible  to  the  naked  eye,  they  are  of 
minor  importance,  unless  it  should  be  found  that  this  is  the  young  of  a 
species  which  changes  with  growth.  The  specimens  yet  seen,  however, 
are  minute,  and  it  may  properly  be  doubted  whether  the  species  attains 


274  SYSTEMATIC  PALEONTOLOGY 

a  size  beyond  the  largest  figures  given.  The  valves  are  often  close  pressed, 
and  deflected  at  the  margin." — Hall,  1847. 

Occurrence. — CHAMBERSBURG  LIMESTONE  (Christiania  bed).  Green- 
castle  and  other  localities  in  southern  Pennsylvania.  Trenton  limestone 
of  New  York. 

Collection. — U.  S.  National  Museum. 

ZYGOSPIRA  MODESTA  (Hall) 
Plate  LIV,  Figs.  20-22;  Plate  LVII,  Figs.  13-16 

Atrypa  modesta  (Say)  Hall,  1847,  Pal.  New  York,  vol.  i,  p.  141,  pi.  xv,  fig.  15. 
Zygospira  modesta  Meek,  1873,  Pal.  Ohio,  vol.  i,  p.  125,  pi.  ii,  fig.  4. 
Zygospira  modesta  Winchell  and  Schuchert,  1893,  Geol.  Minnesota,  vol.  iii, 

p.  465,  pi.  xxxiv,  figs.  42-44. 
Zygospira  modesta  Hall  and  Clarke,  1893,  Pal.  New  York,  vol.  viii,  pt.  2, 

p.  155,  figs.  146-149;  pi.  liv,  figs.  7-10,  12. 

Description. — "  Shell  small,  rather  depressed,  nearly  plano-convex,  sub- 
orbicular,  or  straightened  and  converging  to  the  beaks  at  an  obtuse  angle ; 
lateral  margins  more  or  less  rounded;  front  rounded,  or  sometimes  a  little 
straightened,  or  very  slightly  sinuous  at  the  middle. 

"  Dorsal  valve  with  a  rather  shallow,  undefined  mesial  sinus  of  moderate 
breadth  at  the  front,  but  becoming  rapidly  narrower,  and  less  impressed 
posteriorly,  so  as  often  to  die  out  before  reaching  the  umbo;  surface  on 
each  side  of  the  sinus  gently  convex  centrally,  and  sloping  gradually  to  the 
lateral  margins ;  beak  but  slightly  prominent  and  incurved. 

"  Ventral  valve,  with  a  low  mesial  ridge,  corresponding  to  the  sinus 
of  the  other  valve,  excepting  that  it  is  generally  most  prominent  near  the 
middle,  and  somewhat  depressed  anteriorly;  while  on  each  side  of  the 
ridge  the  slopes  are  distinctly  compressed ;  beak  small,  abruptly  pointed, 
projecting  beyond  that  of  the  other  valve,  and  rather  distinctly  arched; 
but  not  so  closely  incurved  as  to  conceal  the  small  fissure,  which  seems 
to  be  closed  below  by  a  deltidium,  that  leaves  a  minute  aperture  above, 
just  under,  or  extending  to,  the  apex ;  margin  on  each  side  of  beak  cari- 
nated,  so  as  to  give  the  appearance  of  a  kind  of  false  cardinal  area. 


MARYLAND  GEOLOGICAL  SURVEY  275 

"  Surface  of  each  valve  ornamented  by  about  16  to  18  small,  simple, 
radiating  plications,  of  which  about  three  to  five  near  the  front  of  the 
dorsal  valve  occupy  the  mesial  sinus,  the  middle  one  being  usually  a  little 
the  largest;  while  on  the  ventral  valve  about  four  of  the  largest  occupy 
the  mesial  prominence,  the  furrow  between  the  middle  two  being  generally 
a  little  larger  and  deeper  than  the  others ;  marks  of  growth  undefined,  or 
extremely  minute  and  obscure.  Length  of  a  mature,  moderately  large 
specimen,  0.26  inch;  breadth,  0.30  inch;  convexity,  0.15  inch." — Meek, 
1873. 

An  abundant  Cincinnatian  fossil  at  many  localities  in  the  United 
States  and  Canada.  In  Maryland  and  Pennsylvania  the  species  occurs 
in  the  upper  part  (Eden)  of  the  Martinsburg  shale  and  in  the  succeeding 
Fairview  formation. 

Occurrence. — MARTINSBURG  SHALE  (Eden  Division).  Eickard  Moun- 
tain and  Fairview  Mountain,  Washington  County,  Maryland. 

Collections. — Maryland  Geological  Survey,  IT.  S.  National  Museum. 

ZYGOSPIRA  ?  ERRATICA  (Hall) 
Plate  LVII,  Figs.  17-23 

Orthis  f  erratica  Hall,  1847,  Pal.  New  York,  vol.  i,  p.  288,  pi.  Ixxix,  fig.  5. 
Catazyga  erratica  Hall  and  Clarke,  1893,  Pal.  New  York,  vol.  viii,  pt.  2, 
p.  158,  pi.  liv,  figs.  17-23. 

Description. — •"  Subhemispherical,  orbicular ;  dorsal  valve  very  convex, 
with  the  mesial  portion  abruptly  elevated,  flat  above ;  ventral  valve  convex 
at  the  sides,  depressed  in  the  middle,  and  considerably  elevated  in  front ; 
surface  marked  by  fine  simple  uniform  striae." — Hall,  1847. 

This  species  is  readily  distinguished  from  Zygospira  modesta  with 
which  it  is  associated,  by  its  larger  size,  greater  convexity,  and  especially 
by  the  numerous  fine  striae.  A  characteristic  fossil  of  the  Pulaski  shales 
of  New  York  and  Canada. 

Occurrence. — MARTINSBURG  SHALE  (Fairview  division).  Tuscarora 
Mountain,  one  and  one-half  miles  southeast  of  McConnellsburg,  Penn- 
sylvania. 

Collections. — Maryland  Geological  Survey,  TJ.  S.  National  Museum. 


276  SYSTEMATIC  PALEONTOLOGY 

VERMES 

Order  TUBICOLA 

Genus  CORNULITES  Schlotheim 
CORNULITES   FLEXUOSUS    (Hall) 

Plate  LVI,  Fig.  18 

Tentaculites  ?  fiexuosa  Hall,  1847,  Pal.  New  York,  vol.   i,  p.  92,  pi.  xxix, 

figs.  6a-d,  p.  284,  pi.  Ixxviii,  figs.  2a,  b. 
Cornulites  flexuosus  Hall,  1888,  Pal.  New  York,  vol.  vii,  Supp.  1;   p.  18, 

pi.  cxv,  figs.  41,  42. 

Description. — •"  Tubes  single  or  aggregate,  adhering,  more  or  less 
curved  at  the  tip  or  along  the  whole  length ;  surface  marked  by  strong 
ammlations  somewhat  irregular;  interior  distinctly  septate;  septa  with 
the  concave  sides  upwards/' — Hall,  1847. 

Occurrence. — MAETINSBURG  SHALE  (Eden  division).  Jordans  Knob, 
one  and  one-half  miles  northeast  of  Fort  Loudon,  Pennsylvania,  and  Tus- 
carora  Mountain,  two  and  one-half  miles  southeast  of  McConnellsburg, 
Pennsylvania. 

Collections. — Maryland  Geological  Survey,  IT.  S.  National  Museum. 

WORM  BURROWS   (?) 

Genus  SCOLITHUS   Haldemann 

SCOLITHUS  LINEAEIS  (Haldemann)  * 

Plate  XXV,  Fig.  9 

Fucoides  ?  linearis  Haldemann,  1840,  Supp.  Monograph  Limniades,  p.  3. 
Scolithus  linearis  Hall,  1847,  Pal.  New  York,  vol.  i,  p.  2,  pi.  i,  figs,  la-lc. 
Scolithus  linearis  Walcott,  1890,  10th  Ann.  Rep.  U.  S.  Geol.  Surv.,  p.  603, 
pi.  Ixiii,  figs.  1,  la-c. 

Description. — The  pencil-like  fillings  of  the  worm  burrows  to  which 
the  above  name  is  applied  have  a  wide  distribution  in  the  arenaceous 
•Cambrian  rocks  of  Eastern  North  America.  The  species  is  determined 
in  large  part  by  its  geological  position  and  by  the  diameter  of  the  tubes. 
JScolithus  linearis  forms  free  cylindrical  or  subcylindrical,  unbranched, 


MARYLAND  GEOLOGICAL  SURVEY  277 

vermiform  tubes  with  their  surface  usually  smooth,  but  sometimes  appar- 
ently striated.  Their  form  is  rigidly  straight  and  they  range  in  length 
from  several  inches  to  a  foot  or  more.  The  diameter  varies  between  one- 
eighth  to  one-half  an  inch. 

These  tubes  'preserve  their  distinctness  under  almost  all  conditions 
and  they  often  stand  out  quite  clearly  in  the  rock. 

Occurrence. — HARPERS  SHALE  AND  ANTIETAM  SANDSTONE.  In  Mary- 
land this  species  has  been  identified  at  Eakles  Mills  and  other  localities, 
particularly  in  the  drift  blocks  along  the  west  front  of  the  Blue  Ridge. 
Widely  distributed  in  the  Cambrian  of  Pennsylvania,  New  York,  Vir- 
ginia, Canada,  etc. 

Collections. — Maryland  Geological  Survey,  U.  S.  National  Museum. 


order  PRIONODESMACEA 

Family    CTENODONTIDAE 

Genus  CTENODONTA  Salter 
CTENODONTA  GIBBERULA  Salter 

Plate  XLII,  Figs.  18-20 

Ctenodonta  gWberula,  Salter,  1857,  Canadian  Org.  Rem.  Dec.  I,  p.  38,  pi.  viii, 

fig.  6. 
Tellinomya  ventricosa  Meek  and  Worthen,  1868,  Geol.  Surv.  Illinois,  vol.  iii, 

p.  307,  pi.  ii,  figs.  7a-c. 
Ctenodonta  gibberula  Ulrich,   1894,  Geol.  Minnesota,  Pal.,  vol.   iii,  pt.  2, 

p.  587,  pi.  xlii,  fig.  37,  text  figs.  44f-g,  p.  599. 

Description. — "  Shell  rhombic  subovate,  ventricose,  the  height,  length 
and  thickness,  respectively,  as  seven,  ten,  and  six,  with  large  incurved 
beaks,  situated  a  little  behind  the  mid-length ;  antero-dorsal  and  ventral 
margins  subparallel,  the  posterior  end  obliquely  truncate  above  the  narrow 
and  sharply  rounded  lower  part;  anterior  end  broadly  rounded  and  con- 
tinuing into  the  basal  margin ;  the  latter  is  straight  or  very  gently  sinuate 
and  ascends  from  the  prominently  rounded  anterior  part;  posterior 


278  SYSTEMATIC  PALEONTOLOGY 

umbonal  ridge  inconspicuous  in  a  lateral  view,  rather  sharply  defined, 
however,  in  a  dorsal  view  by  a  narrow  furrow  which  outlines  a  wide 
lanceolate  flattened  area,  equally  divided  by  the  hinge  line,  and  in  the 
upper  part  of  which  (immediately  behind  the  beaks)  the  ligament  is 
attached  to  distinct  fulcra;  anterior  dorsal  slope  abruptly  rounded; 
entire  anterior  half  of  valves  strongly  ventricose,  while  between  this  part 
and  the  posterior  umbonal  ridge  a -slight  sulcus  crosses  from  near  the 
beak  to  the  base.  Surface  marked  by  rather  distinct,  closely  arranged, 
subequal  concentric  striae  of  growth,  tending  to  irregularity  in  the  basal 
parts  of  old  shells. 

"  Impressions  of  adductor  muscles  extremely  deep,  the  anterior  pair 
larger  than  the  posterior.  A  small,  though  distinct,  pedal  muscle  scar  is 
always  present  on  the  upper  part  of  the  strong  ridge  which  forms  the 
inner  boundary  of  the  anterior  adductor  (in  casts  it  lies  at  the  bottom  of 
the  deep  cavity  produced  by  this  ridge),  but  the  corresponding  posterior 
scar  is  rarely  distinguishable.  Hinge  plate  very  narrow  at  the  beaks,  but 
widening  rapidly  on  each  side,  the  anterior  half  somewhat  the  stronger 
and  slightly  concave  along  its  inner  margin,  both  terminating  abruptly 
at  the  muscular  scars;  denticles  12  behind  and  10  or  11  in  front,  those 
near  the  beaks  very  small,  all  interlocking  deeply,  especially  those  of  the 
anterior  set,  which  are  also  somewhat  larger  than  the  posterior.  The 
shell  is  very  thick  and  the  rostral  filling  so  considerable  that  in  casts  of 
the  interior  the  beaks  appear  obtuse  and  widely  separated." — Ulrich,  1894. 

A  characteristic  Black  Eiver  species  of  Canada,  New  York,  and  the 
Ohio  and  Mississippi  valleys.. 

Occurrence. — CHAMBERSBUEG  LIMESTONE  (Tetradium  cellulosum 
bed).  Fort  London,  Franklin  County,  Pennsylvania. 

Collections. — Maryland  Geological  Survey,  U.  S.  National  Museum. 

CTENODONTA  OBLIQUA  Hall 
Plate  LIV,  Figs.  17-19 

Nucula  obliqua  Hall,  1845,  Amer.  Jour.  Sci.,  vol.  xliii,  p.  292. 
Tellinomya  ?  oUiqua,  Meek,  1873,  Pal.  Ohio,  vol.  i,  p.  139,  pi.  xi,  figs,  lla-c. 
Ctenodonta  obliqua  Ulrich,   1894,   Geol.  Minnesota,  vol.  iii,  pt.   2,  p.   604, 
pi.  xlii,  figs.  83-87. 


MARYLAND  GEOLOGICAL  SURVEY  279 

Description. — "  Shell  very  small,  compressed,  subcircular,  approaching 
subquadrangular ;  height  and  breadth  about  equal;  anterior  margin  short 
and  rounding  or  less  rounded ;  beaks  elevated,  nearer  the  anterior  margin ; 
dorsal  margin  sloping  from  the  beaks,  the  anterior  slope  being  the  more 
abrupt,  and  the  margin  behind  the  beaks  straighter,  more  compressed  and 
sharper ;  surface  smooth ;  internal  casts  showing  the  muscular  impressions 
to  be  comparatively  rather  distinct.  Hinge  unknown.  Length,  0.06  inch ; 
height  slightly  less;  convexity,  0.03  inch." — Meek,  1873. 

As  indicated  above,  the  hinge  of  this  small  pelecypod  is  unknown,  as 
no  specimens  have  ever  been  found  preserving  the  shell  structure.  Like 
Cyclora  minuta  and  other  dwarfed  gastropods  and  pelecypods,  the 
species  occurs  only  as  phosphatized  casts  or  as  molds  in  the  rock.  Such 
casts  of  C.  obliqua,  however,  occasionally  show  a  denticulated  margin 
along  the  hinge  line  such  as  would  be  left  by  the  denticles  of  a  species  of 
Ctenodonta. 

This  abundant  small  pelecypod  was  described  from  specimens  found  at 
Cincinnati,  Ohio,  but  it  ranges  in  age  from  the  Trenton  to  and  through 
the  Richmond  and  occurs  in  many  states. 

Occurrence. — MARTINSBURG  SHALE  (Eden  division).  Jordans  Knob, 
one  and  one-half  miles  northeast  of  Fort  Loudon,  Pennsylvania. 

Collections. — Maryland  Geological  Survey,  U.  S.  National  Museum. 

CTENODONTA  FILISTRIATA  Ulrich 
Plate  LIV,  Figs.  26-29 

Ctenodonta  filistriata  Ulrich,  1894,  Geol.  Minnesota,  vol.  iii,  pt.  2,  p.  599, 
figs.  44a-e. 

Description. — This  species  has  usually  been  identified  with  the  Trenton 
species  Ctenodonta  levata  Hall,  but  it  may  be  distinguished  from  this  and 
similar  forms  by  the  delicate,  crowded,  thread-like  concentric  lines  which 
cover  the  entire  surface.  Twelve  to  twenty  of  these  lines  may  be  counted 
in  a  space  1  mm.  wide.  This  surface  ornamentation  in  connection  with 
the  subovate  forms  of  the  shell  and  the  rows  of  denticles  on  the  hinge, 
causes  the  species  to  be  easily  recognized. 


280  SYSTEMATIC  PALEONTOLOGY 

Occurrence. — MARTINSBURG  SHALE  (Eden  division).  Jordans  Knob, 
one  and  one-half  miles  northeast  of  Fort  Loudon,  Pennsylvania.  Eden 
shale  at  Cincinnati,  Ohio. 

Collection. — IT.  S.  National  Museum. 

Family    LEDIDAE 

Genus  CLIDOPHORUS  Hall 

CLIDOPHORUS  PLANULATUS  (Conrad) 

Plate  LIV,  Fig.  37 

Nuculites  planulata  Conrad,  1841,  5th  Ann.  Rept.  New  York  Geol.  Surv., 

p.  50. 
Cleidophorus  planulatus  Hall,  1847,  Pal.  New  York,  vol.  i,  p.  300,  pi.  Ixxxii, 

figs.  9a-e. 

Description. — "  Shell  transversely  elliptical  oblong,  height  about  half 
the  length  of  the  shell,  with  the  beak  approximately  a  third  of  the  length 
of  the  shell  from  the  anterior  end.  Umbonal  ridge  low,  distinctly  defined 
along  its  cardinal  border  where  it  makes  an  angle  of  162  to  165  degrees 
with  the  longitudinal  axis  of  the  shell.  Above  this  umbonal  ridge,  the 
posterior  cardinal  slope  of  the  shell  is  flattened  and  subalate.  The  pos- 
terior part  of  the  hinge-line  extends  from  the  beak  for  a  distance  equalling 
about  two-fifths  the  length  of  the  shell,  and  then  makes  an  angle  of  about 
150  degrees  with  the  posterior  margin  of  the  shell.  The  margin  is  rather 
strongly  rounded  at  both  the  posterior  -and  anterior  ends  of  the  shell,  the 
maximum  'curvature  of  the  anterior  margin,  however,  being  nearer  the 
hinge-line.  The  basal  margin  is  moderately  and  evenly  convex.  The 
clavicular  adductor  support  anterior  to  the  beak  forms  an  angle  of  about 
80  degrees  with  the  longitudinal  axis  of  the  shell;  it  is  comparatively 
straight  and  extends  downward  to  about  the  middle  height  of  the  shell ;  it 
is  sharp  and  narrow,  appearing  on  the  cast  of  the  interior  of  the  shell  as  a 
sharp  incision  not  depressing  the  immediately  adjoining  part  of  the  shell. 
The  convexity  of  the  shell  is  moderate,  that  of  a  shell  9  mm.  in  height 
being  about  1.6  mm.  Specimens  20  mm.  in  length  occur." — Foerste,  1914. 


MARYLAND  GEOLOGICAL  SURVEY  281 

Occurrence. — MARTINSBURG  SHALE  (Eden  division).  Eickard  Moun- 
tain, Washington  County,  Maryland.  Eden  shale  and  Maysville  group  of 
New  York  and  Ohio. 

Collection. — U.  S.  National  Museum. 

Family  CYRTODONTIDAE 

Genus    ISCHYRODONTA  Ulrich 
ISCHYRODONTA  UNIONOIDES    (Meek) 

Plate  LVIII,  Figs.  2,  3 

Anodontopsis  ?  unionoides  Meek,  1871,  Amer.  Jour.  Sci.,  vol.  ii,  p.  299. 
Anodontopsis    (Modiolopsis  ?)    unionoides   Meek,    1873,   Pal.   Ohio,   vol.   i, 

p.  141,  pi.  xii,  figs.  2a,  b. 
Ischyrodonta  unionoides  Ulrich,   1893,  Geol.   Surv.   Ohio,  vol.  vii,  p.  677, 

pi.  liv,  figs.  1-3. 
Ischyrodonta  curia  Foerste,  1914,  Bull.  Sci.  Lab.  Denison  Univ.,  vol.  xvii, 

p.  298,  pi.  iii,  fig.  14. 

Description. — "  Shell  of  medium  size,  subovate,  a  little  the  highest 
posteriorly,  compressed,  convex,  thickest  slightly  above  and  in  advance  of 
the  middle.  Anterior  margin  regularly  but  rather  narrowly  rounded; 
base  forming  a  broad  semielliptic  curve;  posterior  margin  broadly 
rounded,  very  slightly  oblique;  dorsal  outline  more  or  less  strongly 
arcuate,  passing  gradually  into  the  ends.  Beaks  small,  compressed,  pro- 
jecting very  little  beyond  the  hinge  margin,  placed  between  one-fourth 
and  one-fifth  of  the  length  of  -the  valves  behind  the  anterior  extremity ; 
umbonal  ridge  scarcely  distinguishable.  Surface  showing  only  a  few  dis- 
tinct subimbri eating  marks  of  growth. 

"  Hinge  comparatively  weak  for  the  genus,  with  one  oblique  cardinal 
tooth  in  the  right  valve  and  two  (?)  in  the  left.  The  ridge-like  internal 
ligament  support  leaves  a  linear  depression  within  the  dorsal  edge  extend- 
ing posteriorly  from  the  beak  for  a  distance  equaling  about  one-third  of 
the  length  of  the  shell.  Anterior  adductor  and  pedal  muscle  attachments 
having  the  characters  usual  for  the  genus,  except  that  they  are,  with 
respect  to  the  beaks,  more  anterior  in  position  for  the  reason  that  the 
anterior  end  is  uncommonly  long." — Ulrich,  1893. 


282  SYSTEMATIC  PALEONTOLOGY 

Occurrence. — MARTINSBURG  SHALE.  (Top  of  the  Fairview  Orthor- 
hynchula  bed)  just  under  the  Oswego  sandstone  on  Tuscarora  Mountain, 
one  and  one-half  miles  southeast  of  McConnellsburg,  Pennsylvania.  Top 
of  the  Fairview  or  base  of  the  McMillan  formation  at  Cincinnati,  Ohio. 
Pulaski  shales  of  New  York  and  Canada. 

Collections. — Maryland  Geological  Survey,  TJ.  S.  National.  Museum. 

Family  AMBONYCHIIDAE 

Genus  BYSSONYGHIA  Ulrich 

BYSSONYCHIA  VEEA  (Ulrich) 

Plate  LIV,  Figs.  34-36 

Byssonychia  vera  Ulrich,  1893,  Geol.  Surv.  Ohio,  vol.  vii,  p.  629,  figs.  a-c. 
Ambonychia  cincinnatiensis  Miller  and  Faber,  1894,  Jour.  Cincinnati  Soc. 
Nat.  Hist.,  vol.  xvii,  p.  24,  pi.  i,  figs.  8-10. 

Description. — This  species  is  quite  similar  to  Byssonychia  radiata. 
(Hall),  the  type  of  the  genus,  and  in  fact  is  frequently  identified  with  it, 
but  B.  vera  differs  in  its  smaller  size,  finer  striae  (there  being  about  50  to 
from  37  to  40  in  the  typical  form  of  that  species),  shorter  hinge  line, 
more  evenly  convex  valves,  and  shorter  byssal  opening. 

Occurrence. — MAETINSBURG  SHALE  (Eden  division).  Southern  Penn- 
sylvania, and  in  the  sandstone  debris  of  Rickard  Mountain,  Maryland. 
Eden  shale  of  the  Ohio  Valley. 

Collections. — Maryland  Geological  Survey,  U.  S.  National  Museum. 

BYSSONYCHIA  RADIATA  (Hall) 
Plate  LVIf,  Fig.  26 

Ambonychia  radiata  Hall,   1847,  Pal.  New  York,  vol.   i,  p.   292,   pi.   Ixxx, 

figs.  4a-l. 
Ambonychia  radiata  Hall  and  Whitfield,  1875,  Geol.  Surv.  Ohio,  Pal.,  vol.  ii, 

p.  79,  pi.  ii,  fig.  2. 
Byssonychia  radiata  Ulrich,  1897,  Geol.  Minnesota,  vol.  iii,  pt.  2,  p.  477, 

fig.  35VI. 
Byssonychia  radiata  Foerste,  1914,  Bull.  Sci.  Lab.  Denison  Univ.,  vol.  xvii, 

p.  273,  pi.  iii,  figs.  12a-c. 

Description. — "  Shell  small  to  medium  sized,  varying  in  outline  from 
subquadrangular,  with  a  rounded  base,  to  acutely  ovate,  according  to  the 


MARYLAND  GEOLOGICAL  SURVEY  283 

degree  of  obliquity  of  the  body  of  the  shell  to  the  direction  of  the  hinge- 
line.  Surface  of  the  shell  ventricose,  and  often  subcarinate  on  the 
umbones  and  towards  the  beaks,  gradually  and  somewhat  regularly  sloping 
to  the  basal  margin,  becoming  attenuate  and  compressed  toward  the 
postero-cardinal  region,  and  abruptly  truncate  and  even  impressed  on  the 
anterior  side.  Beaks  acutely  pointed,  strongly  incurved,  terminal  and 
projecting  above  the  line  of  the  hinge ;  posterior  end  at  right  angles  to  the 
hinge  straight  or  rounded,  or  sometimes  sloping  obliquely  backwards  to 
the  postero-basal  margin ;  base  sharply  rounded.  Anterior  border  of  the 
valves  excavated  below  the  beaks,  forming  a  rather  large  byssal  opening, 
which  is  usually  about  half  as  wide  as  long  when  the  valves  are  united. 

"  Surface  of  the  valves  marked  by  strong,  radiating  ribs,  which  are 
simple  throughout,  strongest  on  the  body  of  the  shell,  and  becoming  finer 
on  the  postero-cardinal  region.  On  the  upper  portion  of  the  shell  the 
ribs  are  flattened  on  the  top,  and  often  grooved  in  the  center,  giving  them 
a  strongly  duplicate  character,  but  becoming  smooth  below,  the  spaces 
between  as  narrow,  or  much  narrower,  than  the  width  of  the  rib.  The  ribs 
are  crossed  by  fine,  concentric,  imbricating  lines  of  growth,  which  undu- 
late as  they  cross  the  elevation." — Hall  and  Whitfield,  1875. 

Occurrence. — MARTINSBURG  SHALE  (Fairview  division).  Tuscarora 
Mountain,  one  and  one-half  miles  southeast  of  McConnellsburg,  Pennsyl- 
vania. Maysville  group  of  the  Ohio  Valley  and  Canada. 

Collections. — Maryland  Geological  Survey,  U.  S.  National  Museum. 

BYSSONYCHIA  PRAECURSA  Ulrich 
Plate  LVII,  Figs.  28,  29 

Byssonychia  praecursa  Ulrich,  1893,  Geol.  Surv.  Ohio,  vol.  vii,  p.  633,  pi.  xlv, 
figs.  1,  2. 

Description-. — In  outline  and  number  of  costae  this  species  is  quite 
similar  to  Byssonychia  radiata  with  which  it  is  associated,  but  it  is  less 
oblique,  the  hinge  is  longer,  and  the  central  part  of  the  valve  is  somewhat 
narrower.  The  marked  difference  between  the  two,  however,  lies  in  the 
flattening  of  the  anterior  side  in  B.  praecursa. 


284  SYSTEMATIC  PALEONTOLOGY 

Occurrence. — MARTLNSBURG  SHALE  (Fairview  division).  Tuscarora 
Mountain,  one  and  one-half  miles  southeast  of  McConnellsburg,  Pennsyl- 
vania. A  characteristic  fossil  of  the  Pulaski  shale  of  New  York  and  of 
the  corresponding  horizon  (Fairview  division  of  the  Maysville  group) 
in  the  Ohio  Valley. 

Collection.— -U.  S.  National  Museum. 

Genus  ALLONYCHIA  Ulrich 

ALLONYCHIA  OVATA  Ulrich 

Plate  LVII,  Fig.  27 

Allonychia  ovata  Ulrich,  1893,  Geol.  Surv.  Ohio,  vol.  vii,  p.  642,  pi.  xlviii, 
figs.  4-6. 

Description. — Shell  large,  55  mm.  in  length  and  36  mm.  wide,  subovate 
but  almost  erect,  strongly  convex.  Hinge  line  short  not  alated  posteriorly 
with  the  beaks  large,  incurved  and  not  terminal.  Surface  marked  with 
40  to  45  radially  arranged  costae.  Hinge  line  short,  edentulous,  with  a 
high  ligamental  area. 

A  fairly  well  preserved  cast  in  sandstone  from  Tuscarora  Mountain, 
Pennsylvania,  exhibited  all  the  characters  of  this  well-marked  species. 

Occurrence. — MARTINSBURG  SHALE  (Fairview  division).  Tuscarora 
Mountain,  one  and  one-half  miles  southeast  of  McConnellsburg,  Penn- 
sylvania. Upper  part  of  Fairview  formation  at  Covington,  Kentucky. 

Collection. — U.  S.  National  Museum. 

Family   AV1CUL1DAE 

Genus  PTERINEA  Goldfuss 

PTERINEA  (CARITODENS)  DEMISSA  (Conrad) 

Plate  LVII,  Fig.  24 

Avicula  demissa  Conrad,  1842,  Jour.  Acad.  Nat.  Sci.  Philadelphia,  vol.  viii, 

p.  242,  pi.  xiii,  figs.  3. 

Avicula  demissa  Hall,  1847,  Pal.  New  York,  vol.  i,  p.  292,  pi.  Ixxxix,  fig.  2a,  b. 
Pterinea  demissa  Hall  and  Whitfield,  1875,  Geol.  Surv.  Ohio,  Pal.,  vol.  ii, 

p.  78,  pi.  ii,  fig.  1. 
Caritodens  demissa  Foerste,  1914,  Bull.  Sci.  Lab.  Denison  Univ.,  vol.  xvii, 

p.  269,  pi.  i,  figs.  10,  pi.  3,  fig.  11. 


MARYLAND  GEOLOGICAL  SURVEY  285 

Description-. — "  Shell  subrhomboidal  in  outline,  with  the  basal  margin 
rounded ;  hinge-line  much  longer  than  the  body  of  the  shell ;  anterior 
wing  extended  into  a  rather  long,  acute  point,  when  perfect,  forming 
nearly  one-third  of  the  length  of  the  hinge,  measured  from  the  point  of 
the  beak ;  posterior  wing  large,  rather  obtusely  pointed,  and  extending  as 
far  as  the  body  of  the  shell  below ;  body  of  the  shell  oblique,  a  line  drawn 
from  the  beak  to  the  center  of  the  base  forming  an  angle  with  the 
posterior  hinge-line  of  about  65  or  70  degrees;  posterior  margin  of  the 
shell  broadly  and  roundly,  but  not  deeply,  excavated  between  the  posterior 
wing  and  the  postero-basal  extremity  of  the  shell;  basal  margin  rather 
sharply  rounded;  anterior  margin  obliquely  sloping  from  the  hinge-line, 
being  nearly  parallel  with  the  body  of  the  shell;  very  slightly  excavated 
below  the  anterior  alation.  Left  valve  strongly  convex  when  not  com- 
pressed, prominent  and  rounded  in  the  center,  but  flattened  and  slightly 
concave  toward  the  alations;  beak  small,  extending  but  little  above  the 
hinge-line;  flattened  or  depressed  convex  on  the  umbo.  Right  valve 
concave,  the  concavity  not  exceeding  one-half  of  the  convexity  of  the 
opposite  valve,  and  usually  somewhat  shorter  on  the  basal  portion. 

"  Surface  of  the'  convex  valve  marked  by  regular,  concentric,  lamellose 
lines,  the  edges  of  which  are  sharply  elevated  when  well  preserved,  giving 
an  exceedingly  roughened  character  to  the  surface.  In  the  degree  of  this 
latter  feature,  as  also  in  the  relative  distance  of  the  lines,  there  is  con- 
siderable variation  in  different  individuals.  Surface  of  the  concave  valve 
distinctly  lamellose,  but  the  precise  features  have  not  been  very  clearly 
determined,  as  no  very  good  specimens  of  this  valve  have  been  examined." 
-Hall  and  Whitfield,  1875. 

A  detailed  description  of  this  species,  particularly  of  the  shell  structure, 
was  given  by  Foerste  in  1914,  but  the  above-quoted  description  applies 
better  to  the  specimens  as  found  in  the  Cumberland  Valley  of  Maryland 
and  Pennsylvania. 

'Occurrence. — MARTIXSBURG  SHALE  (Pairview  division).  Tuscarora 
Mountain,  one  and  one-half  miles  southeast  of  McConnellsburg,  Pennsyl- 
vania. Not  uncommon  in  the  Maysville  and  Richmond  groups  of  the 
Ohio  Valley,  New  York,  and  Canada. 

Collections. — Maryland  Geological  Survey,  IT.  S.  National  Museum. 


286  SYSTEMATIC  PALEONTOLOGY 

Family  LYRODESMIDAE 

Genus  LYRODESMA  Conrad 

LYEODESMA  CONEADI  Ulrich 

Plate  LIV,  Fig.  30 

Lyrodesma  conradi  Ulrich,  1893,  Geol.  Surv.  Ohio,  vol.  vii,  p.  684,  pi.  xlvii, 
fig.  9. 

Description. — "  Shell  a  little  oblique,  transversely  subovate,  somewhat 
the  highest  across  the  middle  of  the  posterior  end;  length  15  to  22  mm., 
height  11.5  to  15  mm.,  thickness  about  half  the  height;  just  beneath  the 
middle  of  the  slightly  oblique  posterior  margin,  the  outline  is  a  little 
produced  and  more  narrowly  rounded  than  elsewhere.  Valves  moderately 
convex,  the  posterior  umbonal  ridge  rounded,  not  a  prominent  feature, 
the  beaks  small,  situated  just  within  the  anterior  third  of  the  length. 
Surface  marked  by  very  fine,  closely  arranged,  sharp  concentric  lines, 
crossed  on  the  posterior  cardinal  slope  by  about  ten  radiating  striae. 
Hinge  with  seven  teeth  of  the  usual  type  in  each  valve.  Adductor  scars 
distinct,  the  posterior  one  rather  small  and  situated  a  very  short  distance 
beneath  the  submarginal  pedal  muscle  impression.  Pallial  line  with  a 
small  though  undeniable  posterior  sinus.  A  peculiar  feature  of  internal 
casts  is  the  broad  and  shallow  furrow  shown  in  the  figure  just  in  front 
of  the  umbonal  ridge." — Ulrich,  1893. 

Occurrence. — MAETINSBUBG  SHALE  (Eden  division).  Jordans  Knob, 
one  and  one-half  miles  northeast  of  Fort  Loudon,  Pennsylvania.  Ederi 
shale  at  Cincinnati,  Ohio. 

Collection. — IT.  S.  National  Museum. 

Family  MODIOLOPSIDAE 

Genus  MODIOLOPSIS  Hall 
MODIOLOPSIS  MODIOLAEIS  (Conrad) 

Plate  LVIII,  Fig.  12 

Pterinea  modiolaris  Conrad,  1838,  2d  Ann.  Kept.   Geol.   Surv.  New  York, 

p.  118. 
Modiolopsis  modiolaris  Hall,   1847,  Pal.  New  York,  vol.  i,  p.  294,  pi.   81, 

figs,  la-g;  pi.  Ixxxii,  fig.  1. 
Modiolopsis  modiolaris  Foerste,  1914,  Bull.  Sci.  Lab.  Denison  Univ.,  vol.  xvii, 

p.  281,  pi.  iii,  fig.  1;  pi.  v,  figs.  1,  2. 


287 

Description. — "  Shell  obliquely  oblong.  The  cardinal  margin  posterior 
to  the  beak  nearly  straight,  rounding  gradually  into  the  oblique  posterior 
margin.  Anterior  to  the  beak,  the  cardinal  margin  is  deflected  down- 
ward, and  then  rounds  into  the  strongly  curved  anterior  margin  of  the 
shell.  Basal  margin  straight  along  that  part  of  the  shell  which  lies 
directly  opposite  the  straight  cardinal  margin;  rising  gradually  toward 
the  curved  anterior  margin,  and  more  rapidly  towards  the  posterior 
margin,  which  is  most  curved  at  the  posterior  extremity  of  the  umbonal 
ridge.  Umbonal  ridge  most  strongly  defined  on  the  cardinal  side  and 
within  about  10  or  15  mm.  from  the  beak,  almost  disappearing  into  the 
general  convexity  of  the  shell  posteriorly.  Mesial  sinus  practically 
obsolete,  although  occasional  specimens  show  a  very  faint  indication  of 
the  same  accompanied  by  a  scarcely  perceptible  concavity  of  the  basal 
outline.  General  convexity  of  the  shell  small.  Concentric  striations  best 
defined  anteriorly,  along  that  part  of  the  shell  which  is  anterior  to  the 
oblique  umbonal  ridge.  Anterior  adductor  depressions  large  and  dis- 
tinctly defined,  although  usually  very  shallow,  owing  to  the  thinness  of 
the  shell.  The  interior  of  one  of  the  valves  is  faintly  striated  posteriorly, 
below  the  umbonal  ridge,  in  a  direction  parallel  to  a  line  drawn  from  the 
posterior  termination  of  the  umbonal  ridge  to  a  point  half  way  between 
the  beak  and  the  upper  anterior  margin  of  the  shell." — Foerste,  1914. 

Numerous  references  have  been  made  to  this  species  in  the  literature 
and  it  has  undoubtedly  been  misidentified  many  times.  The  only  serious 
study  of  this  pelecypod  is  that  in  1914  by  Foerste  whose  description  is 
quoted  above.  Modiolopsis  modiolaris  as  restricted  by  Foerste  is  a  guide 
fossil  of  the  Pulaski  shale  in  New  York  and  in  the  corresponding  hori- 
zons southward  in  the  Appalachians  and  west  to  the  Ohio  Valley. 

Occurrence. — MARTINSBDRG  SHALE  (Fairview  division).  Tuscarora 
Mountain,  one  and  one-half  miles  southeast  of  McConnellsburg,  Penn- 
sylvania. 

Collections. — Maryland  Geological  Survey,  U.  S.  National  Museum. 
19 


288  SYSTEMATIC  PALEONTOLOGY 

Genus  MODIOLODON  Ulrich 

MODIOLODON   TRUNCATUS    (Hall) 

Plate  LVII,  Fig.  25 

Modiolopsis  truncatus  Hall,  1847,  Pal.  New  York,  vol.  i,  p.  296,  pi.  Ixxxi, 

figs.  3a,  b. 
Modiolopsis   truncatus  Hall   and  Whitfield,   1875,   Geol.    Surv.   Ohio,   Pal., 

vol.  ii,  p.  86,  pi.  ii,  fig.  13. 
Modiolodon  truncatus  Ulrich,  1893,  Geol.  Surv.  Ohio,  vol.  vii,  p.  656,  pi.  Ii, 

figs.  9,  10. 

Description. — "  Shell  below  the  medium  size ;  shortly  ovate  in  outline, 
the  widest  part  being  about  one-third  of  the  entire  length  from  the 
posterior  end.  Valves  compressed,  or  depressed  convex,  most  prominent 
near  the  center.  Beaks  small  and  closely  compressed,  scarcely  projecting 
beyond  the  line  of  the  hinge.  Anterior  margin  rather  shortly  rounded, 
the  extremity  extending  but  little  beyond  the  beaks ;  basal  margin  gently 
and  regularly  curving;  posterior  end  more  broadly  rounded  than  the 
anterior  and  most  abruptly  at  the  postero-basal  portion;  above,  it  slopes 
more  gradually  backwards  to  the  extremity  of  the  hinge  line,  with  which 
it  unites  without  forming  any  perceptible  angle. 

"  Surface  of  the  valves  marked  by  irregular,  rather  strong,  concentric 
lines  of  growth. 

"  The  internal  casts — the  condition  in  which  the  species  is  usually 
found  in  the  softer  parts  of  the  formation — show  a  large,  elongate  pos- 
terior muscular  scar,  situated  a  little  within  the  postero-cardinal  margin, 
and  parallel  with  it;  also  a  smaller  lunate  anterior  scar,  and  an  entire 
pallial  line."— Hall  and  Whitfield,  1875. 

Occurrence. — MARTINSBURG  SHALE  (Fairview  division).  Tuscarora 
Mountain,  one  and  one-half  miles  southeast  of  McConnellsburg,  Pennsyl- 
vania. Pulaski  shale  near  Eome,  New  York. 

Collection. — U.  S.  National  Museum-. 


MARYLAND  GEOLOGICAL  SURVEY  289 

Genus  ORTHODESMA  Hall  and  Whitfield 

ORTHODESMA  NASUTUM  (Conrad) 

Plate  LVIII,  Fig.  1 

Cypricardites  nasuta  Conrad,  1841,  5th.  Ann.  Kept.  New  York  Geol.  Surv., 

p.  52. 
Modiolopsis  nasutus  Hall,  1847,  Pal.  New  York,  vol.  i,  p.  159,  pi.  xxxv,  fig.  7, 

p.  296,  pi.  Ixxxi,  fig.  2. 
Orthodesma  nasutum  Foerste,  1914,  Bull.  Sci.  Lab.  Denison  Univ.,  vol.  xvii, 

p.  286,  pi.  iii,  fig.  5;  pi.  5,  fig.  3. 

Description. — This  well-marked  species  is  easily  distinguished  from  all 
associated  pelecypods  by  its  narrow,  subelliptical  form  and  its  anterior 
extremity  drawn  out  into  a  narrow,  quite  extended  nasute  form.  The 
cardinal  margin  of  the  shell  is  distinctly  straight  posterior  to  the  beak, 
but  anterior  to  it  the  margin  drops  so  that  at  its  greatest  departure  it  is 
at  least  3  mm.  lower.  In  its  anterior  portion  the  shell  is  depressed  and 
this,  in  connection  with  the  outline,  adds  to  the  nasute  appearance. 
Posterior  to  the  beak  the  shell  is  more  convex  with  the  areas  of  greatest 
convexity  near  the  cardinal  margin.  The  surface  is  marked  by  indistinct 
concentric  striations  which  are  plainest  along  the  basal  margin  of  the 
anterior  part. 

The  type  specimens  were  secured  from  the  Pulaski  shale  division  of 
the  Lorraine  at  Lorraine,  near  Borne,  etc.,  New  York. 

Occurrence. — MARTINSBURG  SHALE  (Fairview  division).  Tuscarora 
Mountain,  one  and  one-half  miles  southeast  of  McConnellsburg,  Penn- 
sylvania. 

Collection. — U.  S.  National  Museum. 

CLASS  GASTROPODA 
order  ASPIDOBRANCHIA 

Family  PLEUROTOMARIIDAE 

Genus  PLEUROTOMARIA    Defrance 

PLEUROTOMARIA  ?  CANADENSIS  Billings 

Plate  XXXVI,  Figs.  4,  5 

Pleurotomaria  canadensis  Billings,  1865,  Pal.  Fossils,  vol.  i,  Geol.  Surv. 
Canada,  p.  230,  figs.  214,  a,  b. 


290  SYSTEMATIC  PALEONTOLOGY 

Description. — Shell  large,  lenticular  35  to  60  mm.  in  diameter,  consist- 
ing of  six  somewhat  slender  whorls  rising  into  a  depressed  conical  spire. 
Inner  two-thirds  of  whorls  gently  convex;  suture  distinct.  Margin  of 
whorls  sometimes  acute  and  turned  upwards,  sometimes  with  a  rounded 
band.  Just  within  the  margin  is  a  wider  concave  band.  Umbilicus  wide, 
one-half  to  two-thirds  the  shell  diameter,  with  margin  subangular,  and 
the  inner  slope  of  the  whorls  generally  flat.  A  slight  concave  band  just 
beneath  the  margin  on  the  under  side  of  the  whorls.  Aperture  trans- 
versely ovate  or  rhomboidal  with  the  outer  and  inner  angles  acute.  Sur- 
face with  fine,  sharp,  unequal  striae,  usually  with  shallow  undulations 
2  to  4  mm.  wide  conforming  to  the  coarse  of  the  striae ;  all  curving  back- 
wards to  the  margin  and  reaching  it  at  an  acute  angle. 

Occurrence. — BEEKMANTOWN  LIMESTONE  (Ceratopea  zone).  Near 
McConnellsburg  and  other  localities  in  southern  Pennsylvania  and  east 
of  Williamsport  and  near  Halfway,  Maryland. 

Collection. — TJ.  S.  National  Museum. 

PLEUKOTOMAKIA  ?  GEEGAEIA  Billings 
Plate  XXXV,  Figs.  1-3 

Pleurotomaria  gregaria  Billings,  1859,  Canadian  Nat.  Geol.,  vol.  iv,  pp.  355, 
358,  figs.  8h-k. 

Description. — Shell  small,  8  mm.  long  and  5  mm.  wide;  spire  conical 
with  an  apical  angle  of  about  45° ;  three  or  four  whorls.  A  narrow  spiral 
band  is  present.  On  the  body  whorl,  the  band  is  somewhat  above  the 
middle  of  the  volution,  but  in  the  upper  whorls  it  is  situated  on  the  lower 
outer  side  at  about  one-fourth  the  height.  An  obscure  carina  on  the  body 
whorl,  just  above  the  spiral  band,  and  another  close  to  the  suture  is 
present  on  mature  examples;  the  intervening  space  is  flat  or  slightly  con- 
cave. Below  the  band  is  a  third  carina,  scarcely  visible,  and  below  this 
the  whorl  is  rounded  ventricose.  There  is  a  small  umbilicus.  Surface 
minutely  striated. 

This  is  an  interesting  and  well-marked  species,  but  until  a  complete 
revision  of  Beekmantown  gastropods  is  made,  its  generic  position  must 
remain  very  uncertain. 


291 

Occurrence. — BEEKMANTOWN  LIMESTONE  (Turritoma  zone).     Stouf- 
ferstown,  Pennsylvania,  and  east  of  Huyett,  Maryland. 
Collection. — TJ.  S.  National  Museum. 

PLEUROTOMARIA  ?  FLORIDENSIS  Cleland 
Plate  XXXI,  Fig.  6 

Pleurotomaria  floridensis  Cleland,  1900,  Bull.  Amer.  Pal.,  vol.  iii,  p.  125 
(253),  pi.  xv,  fig.  12. 

Description. — Shell  quite  small,  3  mm.  wide  at  the  base  and  4  mm. 
high,  consisting  of  five  slightly  rounded  volutions,  conical,  with  an  apical 
angle  of  44°  and  a  minute  umbilicus. 

Imperfect  casts  and  cross-sections  in  the  rock  of  a  small  conical  shell 
found  occasionally  in  the  Stonehenge  limestone  of  Maryland  seem  to  be 
representatives  of  this  interesting  species  which  hitherto  has  been  noted 
only  in  the  corresponding  horizon  in  New  York.  The  reference  of  this 
species  to  Pleurotomaria  is  known  to  be  incorrect,  but  in  the  present  state 
of  our  knowledge  of  Canadian  gastropods  it  is  useless  to  attempt  more 
accurate  generic  determination.  The  specimens  found  in  Maryland  are 
not  well  enough  preserved  for  a  critical  study  of  their  generic  characters. 

Occurrence. — BEEKMANTOWN  LIMESTONE  (Sttoehenge  member). 
Vicinity  of  Hagerstown,  Maryland.  Tribes  Hill  limestone  of  New  York. 

Collection. — U.  S.  National  Museum. 

Genus  HORMOTOMA    Salter 
HORMOTOMA  ARTEMESIA  (Billings) 

Plate  XXXVI,  Figs.  8,  9 

Murchisonia   artemesia   Billings,    1865,    Pal.    Fossils,   vol.    i,    Geol.    Surv. 
Canada,  p.  345,  fig.  332. 

Description. — Shell  elongate,  varying  from  50  to  75  mm.  in  length, 
slender,  consisting  of  10  to  12  depressed  convex  whorls  with  a  strong, 
rounded  spiral  band.  In  casts  the  whorls  are  depressed  ventricose, 
flattened  in  the  middle  and  abruptly  rounded  in  the  deep  suture.  Casts 
of  the  exterior  show  a  strong,  rounded  band  along  the  median  line  of  the 


292  SYSTEMATIC  PALEONTOLOGY 

whorls  about  2  mm.  wide  on  the  large  whorls.  Surface  with  fine,  sharp 
striae  curving  backwards  to  the  band. 

The  elongate,  slender  form  of  this  shell  and  the  band  along  the  median 
line  of  the  whorls  are  sufficient  characters  to  discriminate  it  from  other 
associated  forms  of  gastropods. 

Occurrence. — BEEKMANTOWN  LIMESTONE  (Ceratopea  zone).  Appa- 
lachian Valley  in  Pennsylvania,  Maryland,  and  Virginia.  Natural  sections 
and  poorly  preserved  casts  of  this  species  occur  in  the  exposures  east  of 
Williamsport  and  in  the  vicinity  of  Halfway,  Maryland. 

Collections. — Maryland  Geological  Survey,  U.  S.  National  Museum. 

HOBMOTOM A  GRACILIS  (Hall) 

Plate  LV,  Figs.  7,  8 

Murchisonia  gracilis  Hall,  1847,  Pal.  New  York,  vol.  i,  p.  181,  pi.  xxxix, 

figs.  4a-c;  p.  303,  pi.  Ixxxiii,  figs.  la-b. 
Hormotoma  gracilis  Ulrich  and   Scofield,   1897,   Geol.  Minnesota,  vol.   iii, 

pt.  2,  p.  1015,  pi.  Ixx,  figs.  18-21. 

Description  (typical  form). — "  Height  20  to  33  mm.,  apical  angle  very 
constantly  about  18°.  Shell  small,  slender;  volutions  about  14  in  a 
length  of  30  mm. ;  rounded  generally  with  a  slight  angulation,  on  which 
lies  the  band,  a  little  beneath  the  middle;  band  seldom  preserved,  when 
perfect,  rather  narrow,  smooth,  flat  or  faintly  concave  and  margined  on 
each  side  by  a  delicate  raised  line;  suture  simple,  deep;  lines  of  growth 
fine,  bending  strongly  backward  from  the  suture  to  the  band,  and  beneath 
this  curving  very  strongly  forward  again,  the  whole  indicating  a  deeply 
notched  mouth ;  aperture  a  little  higher  than  wide,  rounded  except  below 
where  it  is  somewhat  produced;  inner  lip  reflected,  forming  a  slightly 
twisted  and  thickened  columella." — Ulrich  and  Scofield,  1897. 

Widely  distributed  in  the  United  States  and  Canada  in  rocks  ranging 
from  the  Trenton  to  and  through  the  Eichmond. 

Occurrence. — MARTINSBUKG  SHALE  (Eden  division).  Fort  Loudon, 
Pennsylvania,  and  the  west  slope  of  Eickard  Mountain,  Washington 
County,  Maryland. 

Collections. — Maryland  Geological  Survey,  U.  S.  National  Museum. 


MARYLAND  GEOLOGICAL  SURVEY  293 

HORMOTOMA  GRACILENS   (Whitfield) 

Plate  XXXV,  Figs.  4,  5 

Murchisonia  gracilens  Whitfleld,  1889,  Bull.  Amer.  Mus.  Nat.  Hist,  vol.  ii, 
p.  53,  pi.  viii,  figs.  14,  15. 

Description. — Shell  rather  small,  possibly  reaching  25  mm.  in  length, 
and  very  slender  with  the  apical  angle  not  more  than  16  to  18  degrees, 
consisting  of  numerous  whorls,  six  of  which  occur  in  the  upper  part  of  the 
spire  of  a  small  individual  in  6  mm.  Volutions  ventricose,  smooth  or 
with  but  a  very  slight  angularity  near  the  middle  of  the  exposed  portion ; 
sutures  deep  and  strongly  marked.  Columella  and  aperture  unknown. 

This  species  is  probably  the  Canadian  representative  of  the  abundant 
Middle  and  Upper  Ordovician  Hormotoma  gracilis  Hall  which  it  greatly 
resembles.  The  earlier  species,  however,  is  a  trifle  more  slender. 

Occurrence. — BEEKMANTOWN  LIMESTONE  (Turritoma  zone).  Stouf- 
ferstown,  Pennsylvania,  and  near  Huyett,  Maryland. 

Collections. — Maryland  Geological  Survey,  U.  S.  National  Museum. 

Genus  TURRITOMA    Ulrich 
TURRITOMA  ACREA  (Billings) 

Plate  XXXV,  Fig.  11 

Murchisonia  acrea  Billings,  1865,  Pal.  Foss.,  vol.   i,  Geol.   Surv.  Canada, 
p.  232,  text  fig.  216. 

Description. — Shell  rather  small  and  slender,  about  25  mm.  long  and 
7  mm.  at  its  widest  portion,  resembling  a  Turritella;  apical  angle  15°  to 
20° ;  whorls  12  to  15  in  number,  flat  or  subconcave,  each  with  the  lower 
edge  angularly  rounded  and  projecting  slightly  over  the  one  below; 
surface  above  this  projection  flat  or  gently  concave;  and  sloping  to  the 
suture,  near  which  is  a  slight  convexity.  Surface  characters  unknown. 

This  shell  is  easily  recognized  even  in  poor  specimens  by  its  consider- 
able resemblance  to  a  small  species  of  Turritella.  Its  characters  are  so 
distinctive  that  Ulrich  selected  it  as  the  type  of  his  genus  Turritoma. 


294  SYSTEMATIC  PALEONTOLOGY 

Occurrence. — BEEKMANTOWN  LIMESTONE  (Turritoma  zone).  Stouf- 
ferstown,  Pennsylvania,  and  east  of  Huyett,  Maryland.  Canadian 
(Division  G  of  the  Quebec  group),  Port  aux  Choix,  Newfoundland. 

Collection. — TJ.  S.  National  Museum. 

Genus  LOPHOSPIRA    Whitfield 
LOPHOSPIEA  BICINCTA   (Hall) 

Plate  XXXIX,  Figs.  1-5 

Murchisoriia  bicincta  Hall,  1847  (not  McCoy,  1844),  Pal.  New  York,  vol.  i, 

p.  177,  pi.  xxxvili,  figs.  5a-f  (?  5g  and  5h). 
Lophospira  bicincta  Ulrich  and  Scofield,  1897,  Geol.  Minnesota,  Pal.,  vol.  iii, 

pt.  2,  p.  964,  pi.  Ixxii,  figs.  1-5. 

Description. — "  Hight  15  to  30  mm.;  apical  angle  59°  to  63°,  usually 
about  60°.  Volutions  five  or  six,  subangular;  last  one  ventricose  below, 
tricarinate,  the  upper  ones  bicarinate,  the  lower  carina  being  hidden  by  the 
suture;  central  or  peripheral  angle  margined  on  either  side  by  a  sharp 
elevated  line,  with  a  narrow  groove  between,  the  angle,  therefore,  being 
composed  of  three  lines  of  which  the  central  one  is  a  little  stronger  and 
more  prominent  than  the  lateral  ones ;  lower  carina  thin,  abruptly  raised, 
the  space  between  it  and  the  peripheral  angle  scarcely  concave  and  almost 
perpendicular ;  upper  carina  sharp,  rather  strong,  removed  a  little  more 
than  a  third  of  the  biconcave  upper  slope  of  the  volution  from  the  suture ; 
aperture  somewhat  obliquely  subelliptical,  higher  than  wide,  narrow 
below,  subangular  at  the  lower  inner  corner ;  inner  lip  but  little  thickened, 
slightly  twisted,  never  completely  covering  the  minute  umbilicus;  outer 
lip  very  slightly  sinuate.  Surface  marked  by  fine,  sharp,  subequal  striae, 
curving  backward  very  gently  from  the  suture  to  the  peripheral  band; 
beneath  the  latter  they  pass  in  a  vertical  direction  to  the  lower  carina 
which  scarcely  interrupts  their  course  to  the  umbilicus,  near  which  only  a 
slight  backward  curve  is  noticeable.  On  the  most  perfect  specimen  seen 
all  the  transverse  lines  present  the  appearance  of  being  minutely  papillose 
or  toothed,  while  the  central  line  of  the  peripheral  band  is  crossed  by 
straight  lines,  of  which  there  are  nearly  twice  as  many  in  a  given  space  as 
of  those  coming  from  above  and  below. 


MARYLAND  GEOLOGICAL  SURVEY  295 

"  The  most  marked  and  important  feature  of  this  species  is  the  exceed- 
ing shallowness  of  the  sinus  or  notch  in  the  outer  lip.  The  essential 
characters  of  L.  bicincta,  as  here  identified  and  restricted,  are  (1)  the 
ventricose  whorls,  (2)  the  sharp  and  regular  lines  of  growth,  and  (3)  the 
exceedingly  shallow  sinus  in  the  outer  lip  and  vertical  direction  of  the 
surface  striae  from  the  peripheral  band  downward." — Ulrich  and  Sco- 
field,  1897. 

Occurrence. — STONES  EIVER  LIMESTONE.  Old  quarry  at  Chambers- 
burg,  Pennsylvania,  and  south  into  Maryland.  The  original  types  are 
from  the  Trenton  of  New  York,  but  the  species  is  said  to  range  from  the 
Stones  Eiver  to  the  Richmond. 

Collections. — Maryland  Geological  Survey,  U.  S.  National  Museum. 

LOPHOSPIRA   (RUEDEMANNIA)    LIRATA   (Ulrich) 

Plate  LY,  Figs.  5,  6 

LopJiospira  (f  Seelya)   lirata  Ulrich,  1897,  Geol.  Minnesota,  vol.  iii,  pt.  2, 

p.  998,  pi.  Ixxii,  figs.  56-59. 
Ruedemannia  lirata  Foerste,  1914,  Bull.  Sci.  Lab.  Denison  Univ.,  vol.  xvii, 

p.  312. 

Description. — "  Hight  15  to  24  mm.,  apical  angles  65°  to  70°,  the 
angle  of  the  first  three  whorls  usually  a  little  wider.  Volutions  about 
five  and  a  half,  ventricose,  the  carinae  not  greatly  interfering  with  the 
general  roundness  of  their  outlines.  Peripheral  band  median,  appearing 
lower  on  the  whorls  of  the  spire,  very  slightly  prominent,  trilineate;  the 
lines  of  equal  strength  and  elevation  or  the  median  one  is  a  little  weaker 
and  not  as  sharply  defined  as  the  margined  ones.  About  midway  between 
the  band  and  the  suture  lines  a  small  ridge  or  carina  divides  the  upper 
slope  into  two  flat  or  slightly  concave  spaces.  Nearly  the  same  distance 
beneath  the  lower  margin  of  the  band  in  the  typical  form  of  the  species 

we  meet  with  the  first  and  strongest  of  about  eight  revolving  ribs 

Umbilicus  exceedingly  small,  sometimes  closed  by  a  slight  overlap  of  the 
inner  lip.  Aperture  subovate,  rounded  below  and  rather  straight  at  the 
inner  side.  Lines  of  growth  sharp,  thread-like,  regular,  either  fine  and 


296  SYSTEMATIC  PALEONTOLOGY 

equal  on  all  parts  of  a  whorl  or  they  may  be  farther  apart  with  interpola- 
tions on  the  upper  slope.  The  lunulae  of  the  band  are  fine  and  regularly 
curved."— Ulrich,  1897. 

Occurrence. — MARTINSBURG  SHALE  (Eden  division).  Jordans  Knob, 
one  and  one-half  miles  northeast  of  Fort  Loudon;  Tuscarora  Mountain, 
two  and  one-half  miles  southeast  of  McConnellsburg ;  and  Cowan  Gap,  five 
miles  northeast  of  McConnellsburg,  Pennsylvania.  Fragmentary  casts 
of  this  species  were  noted  in  the  sandstone  debris  of  the  Upper  Martins- 
burg  on  the  west  slope  of  Eickard  Mountain,  Washington  County,  Mary- 
land. 

Collection. — U.  S.  National  Museum. 

Genus  LIOSPIRA  Ulrich  and  Scofield 
LlOSPIEA  MICULA   (Hall) 

Plate  LVIII,  Figs.  7-9;  Plate  LV,  Figs.  25,  26 

Pleurotomaria  micula  Hall,  1862,  Geol.  Kept.  Wisconsin,  p.  55,  fig.  1. 
Liospira  micula  Ulrich  and  Scofield,  1897,  Geol.  Minnesota,  vol.  iii,  pt.  2, 
p.  994,  pi.  Ixviii,  figs.  24-29. 

Description. — Shell  discoidal  and  small,  rarely  exceeding  16  mm.  in 
diameter  and  usually  11  or  12  mm.,  with  the  umbilicus  filled  by  a  reflexed 
callosity  of  the  inner  lip.  Externally  this  filling  is  concave,  smooth  and 
distinct  from  the  finely  striated  under  side  of  the  volutions.  The  shell 
has  four  volutions  with  such  shallow  sutures  that  the  spire  forms  an 
almost  even  slope  from  its  apex  to  the  periphery.  Surface  marked  with 
fine  lines  of  growth  and  in  the  best  preserved  specimens  with  very  delicate 
revolving  lines.  On  the  under  side  the  lines  of  growth  are  broadly  curved 
with  the  greatest  curvature  on  the  inner  half.  The  band  is  obliquely 
placed  on  the  periphery  and  most  visible  on  the  upper  side. 

This  is  one  of  the  long  ranging  gastropods,  specimens  apparently  the 
same  as  the  types,  which  come  from  the  Richmond  (Maquoketa)  of  Wis- 
consin, being  found  in  all  the  formations  from  the  Trenton  to  and 
through  the  Eichmond. 

The  usual  specimens  found  are  seldom  well  preserved  and  it  is  possible 
that  with  better  material  differences  may  be  noted  in  examples  from  the 
various  horizons. 


MARYLAND  GEOLOGICAL  SURVEY  297 

Occurrence. — MARTIXSBURG  SHALE  (Eden  and  Fairview  divisions). 
Jordans  Knob,  one  and  one-half  miles  northeast  of  Fort  Loudon,  Penn- 
sylvania, and  the  west  slope  of  Bickard  Mountain,  Washington  County, 
Maryland,  have  afforded  poorly  preserved  specimens. 

Collection. — U.  S.  National  Museum. 

Family  EUOMPHALIDAE    Dekoninck 

Genus  MACLURITES  Lesueur 

MACLURITES  AFFINIS  (Billings) 

Plate  XXXIII,  Figs.  8,  9 

Maclurea  afflnis  Billings,  1865,  Pal.  Fossils,  vol.  i,  Geol.  Surv.  Canada,  p.  238, 

text  figs.  224a,  b. 
Maclurea  afflnis  Whitfield,  1897,  Bull.  Amer.  Mus.  Nat.  Hist,  vol.  ix,  p.  180, 

pi.  iv,  figs.  8,  9. 

Description. — Shell  35  to  50  mm.  in  width  and  12  to  16  mm.  in  height 
with  a  flat  spire  of  four  or  five  slender  whorls,  uniformly  convex  on  the 
upper  side,  and  with  deeply  impressed  sutures.  Umbilicus  about  three- 
fifths  the  width  of  the  shell,  with  the  edge,  as  shown  in  a  vertical  sec- 
tion, acute ;  the  inner  sides  of  the  whorls,  in  the  umbilicus,  convex.  Sur- 
face unknown. 

Occurrence. — BEEKMANTOWN  LIMESTONE  (Cryptozoon  steeli  zone). 
Vicinity  of  Hagerstown  and  Williamsport,  Maryland.  Canadian  of 
Newfoundland  and  Vermont. 

Collection. — TJ.  S.  National  Museum. 

MACLURITES  MAGNUS  Lesueur 

Plate  XXXIX,  Figs.  12-15 

Maclurites  magna  Lesueur,  1818,  Jour.  Acad.  Nat.  Sci.  Philadelphia,  vol.  i, 

p.  312,  pi.  xiii,  figs.  1-3. 
Maclurea  magna  Hall,  1847,  Pal.  New  York,  vol.  i,  p.  26,  pi.  v,  figs,  la-e; 

pi.  v,  (bis),  figs.  la-c. 
Maclurites  magnus  Raymond,  1908,  Ann.  Carnegie  Mus.,  vol.  iv,  p.  199,  pi.  1, 

figs.  1,  2;  pi.  li,  figs.  1,  2;  pi.  lii,  figs.  1-4. 

Description. — "  Sinistrorsal,  discoidal,  depressed  turbinate ;  breadth 
more  than  twice  as  great  as  the  height ;  spire  flat,  a  slightly  depressed  line 


298  SYSTEMATIC  PALEONTOLOGY 

at  the  sutures;  whorls  about  six,  gradually  increasing  from  the  apex, 
ventricose,  flattened  above,  obtusely  angular  on  the  outer  edge;  surface 
marked  by  fine  striae,  which  upon  close  examination,  are  found  to  be 
produced  by  the  imbricating  edges  of  lamellae ;  striae  undulating,  bending 
backwards  from  the  suture  and  forward  in  passing  over  the  edge  of  the 
shell;  aperture  obtusely  trigonal,  depressed  above,  slightly  expanded 
beyond  the  dimensions  of  the  whorl  just  behind  it ;  axis  hollow,  umbilicus 
broad  and  deep,  extending  to  the  top  of  the  spire." — Hall. 

Associated  with  the  large  shell  of  this  Maclurites  is  an  operculum 
which  undoubtedly  belongs  to  the  species.  It  is  large,  heavy,  and  horn- 
shaped  and  has  the  nucleus  twisted  to  the  right.  In  the  inner  right-hand 
corner  of  the  operculum,  as  may  be  noted  in  fig.  15,  of  pi.  XXXIX,  there 
is  a  long  process  projecting  downward  into  the  shell  and  forming  a  place 
for  attachment  of  muscles. 

Occurrence. — STONES  EIVER  LIMESTONE  (Middle  division).  Many 
localities  in  southern  Pennsylvania;  Pinesburg,  etc.,  Maryland.  An 
abundant  and  characteristic  fossil  of  the  Middle  Chazyan  from  Montreal. 
Canada,  to  east  Tennessee,  the  original  types  coming  from  the  Lake 
Champlain  area.  In  Tennessee  the  species  is  so  abundant  in  the  Lenoir 
limestone  that  this  formation  has  been  termed  the  Maclurea  limestone. 

Collections. — Maryland  Geological  Survey,  U.  S.  National  Museum. 

MACLURITES  SORDIDUS  (Hall) 
Plate  XXXVI,  Figs.  1-3 

Maclurea  sordida  Hall,  1847,  Nat.  Hist.  New  York,  Pal.,  vol.  i,  p.  10,  pi.  iii, 
figs.  2,  2a. 

Description, — Shell  subdiscoidal ;  consisting  of  two  to  two  and  a  half 
slightly  disconnected  whorls  rapidly  increasing  in  diameter,  strongly 
rounded  on  the  upper  side  with  deeply  sunken  apex,  flattened  on  the 
lower  side,  and  the  peripheral  edge  rather  sharply  rounded.  Aperture 
semicircular.  Shell  thick,  the  surface  usually  with  only  faint  lines  of 
growth,  but  sometimes  strong,  transverse  striae,  with  more  distant 
undulations.  The  transverse  lines  of  growth  curve  forward  on  the  lower 
flattened  surface  and  backward  on  the  rounded  upper  surface. 


MARYLAND  GEOLOGICAL  SURVEY  299 

Occurrence. — BEEKMANTOWN  LIMESTONE  (Ceratopea  zone).  Casts 
and  section  of  the  shall  may  be  observed  at  this  horizon  west  of  Hagers- 
town,  and  also  in  several  exposures  east  of  Williamsport,  Maryland. 
Beekmantown  of  New  York  and  Vermont. 

Collection. — U.  S.  National  Museum. 

MACLURITES  OCEANUS  (Billings) 
Plate  XXXV,  Figs.  7,  8 

Maclurea  oceana  Billings,  1865,  Pal.  Fossils,  vol.  i,  Geol.   Surv.  Canada, 
p.  237,  text  fig.  223a,  b. 

Description. — Shell  varying  from  25  mm.  to  100  mm.  in  diameter, 
consisting  of  four  or  five,  rather  slender  whorls  with  an  umbilicus  measur- 
ing about  half  the  whole  width  in  the  small  specimens.  Spire  flat;  the 
outer  edge  narrowly  rounded;  the  suture  deeply  impressed  in  the  usual 
specimens,  casts  of  the  interior,  but  compressed  and  thread-like  when  the 
shell  is  preserved.  Outer  side  of  the  body-whorl  gently  convex,  and 
sloping  to  the  edge  of  the  umbilicus  at  an  angle  of  from  60°  to  70°  with 
the  plane  of  the  flat  side  of  the  shell.  Aperture  a  little  less  than  half  the 
whole  width  of  the  shell  in  height.  Edge  of  umbilicus  acutely  rounded ; 
inner  side  of  the  whorls  in  the  umbilicus  gently  convex,  and  somewhat 
sloping  with  the  edge  exposed  to  the  apex.  Surface  unknown,  but  most 
probably  finely  striated. 

Occurrence. — BEEKMANTOWN  LIMESTONE  (Turritoma  zone).  Natural 
sections  of  this  shell  were  noted  in  the  exposures  along  the  National  High- 
way east  of  Huyett,  Maryland.  Canadian  of  Newfoundland. 

Collection. — U.  S.  National  Museum. 

Genus  CERATOPEA    Ulrich 
CERATOPEA  KEITHI  Ulrich 

Plate  XXXVI,  Fig.  15 

Operculum  of  f  Maclurea  Bassler,  1909,  Bull.  Geol.  Surv.  Virginia,  vol.  iia, 

pi.  xx,  fig.  3. 
Ceratopea  keithi  Ulrich,  1911,  Bull.  Geol.  Soc.  Amer.,  vol.  xxii,  No.  3,  p.  665. 


300  SYSTEMATIC  PALEONTOLOGY 

Description. — The  above  name  has  been  employed  for  an  unusual  type 
of  operculum  supposed  to  belong  to  some  spiral  shell  like  Madurea.  The 
particular  gastropod  possessing  such  a  thick  closure  to  the  shell  is  un- 
known. Possibly  the  shell  was  of  such  a  nature  that  it  was  easily  de- 
stroyed, but  the  opercula  occur  often  in  considerable  numbers.  Several 
distinct  types  of  these  opercula  are  known,  but  each  holds  its  own  par- 
ticular form  and  marks  a  definite  stratigraphic  horizon.  The  one  to  which 
the  name  Ceratopea  keithi  has  been  given,  marks  a  zone  in  the  Middle 
Beekmantown  throughout  the  Appalachian  Valley,  and  as  specimens  are 
usually  common,  this  species  is  regarded  as  such  an  exceptionally  valuable 
guide  fossil  that  the  name  Ceratopea  zone  has  been  applied  to  the  strata 
containing  it.  The  various  aspects  of  the  species  are  illustrated  in  enough 
detail  on  pi.  XXXVI  to  make  its  identification  certain. 

Occurrence.— BEEKMANTOWN  LIMESTONE  (Ceratopea  zone).  Several 
localities  northeast  and  southwest  of  Halfway,  Maryland,  afford  silicified 
specimens  of  this  fossil.  A  common  and  characteristic  fossil  of  the  Middle 
Beekmantown  in  the  Appalachian  Valley  from  Pennsylvania  to  Alabama. 

Collections. — Maryland  Geological  Survey,  U.  S.  National  Museum. 

Genus  HELIGOTOMA  Salter 

HELICOTOMA  PLANULATOIDES  Ulrich 

Plate  XLII,  Figs.  13-15 

Helicotoma  planulatoides  Ulrich,  1897,  Geol.  Minnesota,  Pal.,  vol.  iii,  pt.  2, 
p.  1034,  pi.  Ixxiv,  figs.  28-30. 

Description. — This  species  is  closely  related  to  the  widespread  Black 
River  species  Helicotoma  planulata  Salter,  but  differs  in  that  it  has  only 
about  four  whorls  instead  of  five  and  each  descends  slightly  below  the 
level  of  the  preceding.  The  umbilicus  is  somewhat  narrower  than  in 
H.  planulata  and  revolving  lines  are  totally  absent.  Specimens  range  in 
width  from  15  to  25  mm. 

Occurrence. — CHAMBERSBURG  LIMESTONE  (Tetradium  cellulosum 
bed).  Fort  Loudon,  Franklin  County,  Pennsylvania.  Lowville  limestone 
of  Kentucky  and  Tennessee. 

Collection. — U.  S.  National  Museum. 


301 

HELICOTOMA  VERTICALIS  Ulrich 
Plate  XL1I,  Figs.  16,  17 

Helicotoma  verticalis  Ulrich,  1897,   Geol.   Minnesota,   Pal.,  vol.  iii,   pt.  2, 
p.  1035,  pi.  Ixii,  fig.  69;  pi.  Ixxiv,  figs.  18  and  19. 

Description. — This  shell,  although  known  only  from  casts  of  the  in- 
terior, is  so  well  characterized  by  the  rectangular  form  of  the  outer  and 
upper  surfaces  of  the  whorls  that  it  should  be  easily  recognized.  The 
whorls  are  not  more  than  four  in  number,  enlarge  rapidly,  are  strongly 
convex  below  and  leave  a  deep  and  relatively  narrow  umbilicus.  On  the 
under  side  the  cast  resembles  the  shell  of  Helicotoma  planulatoides  quite 
closely,  but  otherwise  the  two  species  are  quite  different,  as  the  outer  side 
of  the  whorls  in  the  latter  are  concave  and  inclined  inward  above  instead 
of  convex  or  flat  and  vertical. 

Occurrence. — CHAMBERSBURG  LIMESTONE  (Tetradium  cellulosum 
bed).  Fort  Loudon,  Franklin  County,  Pennsylvania.  Lowville  lime- 
stone of  Kentucky. 

Collection. — U.  S.  National  Museum. 

Genus  ECCYLIOPTERUS  Remele 
ECCYLIOPTEEUS  DISJUNCTUS  (Billings) 

Plate  XXXV,  Figs.  9,  10 

OpMleta  ?  disjuncta  Billings,  1865,  Pal.  Foss.,  vol.  i,  Geol.  Surv.  Canada, 
p.  344,  text  fig.  331a,  b. 

Description. — Shell  about  25  mm.  in  diameter,  consisting  of  two  or 
three  whorls  slightly  separated  from  each  other  and  with  a  strongly 
elevated,  sharp  carina.  Spire  deeply  concave;  carina  located  one-third 
the  width  from  the  outer  margin.  Within  the  carina  there  is  first  a 
shallow  concave  band,  and  then  a  concave  slope  into  the  suture ;  without 
it  is  a  little  defined  concavity,  below  which  the  periphery  is  uniformly 
convex.  The  whorls  on  the  under  side  vary  from  uniformly  to  depressed 
convex,  sometimes  becoming  flat  near  the  aperture  along  the  median  line. 
Depth  and  width  of  whorls  about  equal,  greatest  amount  of  separation 
of  whorls  about  4  mm.  Surface  with  rather  strong,  scale-like  striae. 


302  SYSTEMATIC  PALEONTOLOGY 

Occurrence. — BEEKMANTOWN  LIMESTONE  (Turritoma  zone).  Stouf- 
ferstown,  Pennsylvania,  and  in  exposures  along  the  National  Highway, 
east  of  Huyett,  Maryland.  Beekmantown  limestone  of  Canada. 

Collection. — TJ.  S.  National  Museum. 

ECCYLIOPTEEUS  TEIANGULUS    (Whitfield) 

Plate  XXXIII,  Figs.  6,  7 

Ecculiomphalus  triangulus  Whitfield,   1890,  Bull.  Amer.  Mus.  Nat.   Hist., 

vol.  iii,  p.  29,  pi.  i,  figs.  5-9. 
Eccyliopterus  triangulus  Ulrich  and  Scofield,  1897,  Geol.  Minnesota,  Pal., 

vol.  iii,  pt.  2,  pi.  Ixxiv,  figs.  5,  6;  pi.  Ixii,  fig.  73. 

Description. — Shell  less  than  two  inches  in  diameter  and  consisting  of 
from  one  to  one  and  a  half  volutions,  loosely  coiled  and  not  in  contact  at 
any  point.  Tube  increasing  rather  rapidly  in  dimensions,  triangular  in 
section,  flattened  on  three-fourths  of  its  upper  surface  and  rapidly 
rounded  to  the  inner  angle.  Peripheral  angle  acute  and  the  outer  surface 
sloping  rapidly  inward  to  the  rounded  basal  angle.  Shell  substance  very 
thin,  the  surface  characters  unknown,  except  indistinct  wavy  lines  cross- 
ing the  shell  and  receding  toward  the  acute  angle.  The  apical  portion  is 
usually  entirely  filled  with  calcareous  matter  as  the  shell  gets  larger,  thus 
shortening  the  inner  coil  of  the  casts. 

Occurrence. — BEEKMANTOWN  LIMESTONE  (Cryptozoon  steeli  zone). 
Three-fourths  mile  east  of  Charlton,  Maryland,  and  at  the  same  horizon 
in  Pennsylvania.  The  types  are  from  this  formation  in  Vermont. 

Collection. — U.  S.  National  Museum. 

Genus  OPHILETA  Vanuxem 

OPHILETA  COMPLANATA  Vanuxem 

Plate  XXXI,  Figs.  2-5 

Ophileta  complanata  Vanuxem,  1842,  Nat.  Hist.  New  York,  Geol.,  vol.  iii, 

p.  36,  fig.  2. 

Ophileta  complanata  Cleland,  1903,  Bull.  Amer.  Pal.,  vol.  iv,  p.  15  (41). 
Pleurotomaria  hunterensis  Cleland,  1900,  Bull.  Amer.  Pal.,  vol.  iii,  p.  124 

(252),  pi.  xvii,  figs.  1,  2,  7,  8. 
Pleurotomaria  Jiunterensis  Cleland,  1903,  Bull.  Amer.  Pal.,  vol.  iv,  p.  16, 

pi.  iv,  figs.  1,  2. 


MARYLAND  GEOLOGICAL  SURVEY  303 

Description. — Shell  conical,  varying  from  10  mm.  to  40  mm.  in  width, 
consisting  of  six  or  more  volutions  elevated  into  a  spire  and  with  an 
umbilicus  about  one-half  as  wide  as  the  entire  diameter.  Upper  surface 
of  shell  nearly  flat  with  a  faint  groove  near  the  edge;  under  surface 
slightly  angulate.  Aperture  irregularly  rhomboidal. 

Under  the  name  of  Ophileta  complanata  a  number  of  distinct  species 
of  Canadian  gastropods  has  been  classed  in  the  past  half  century  and  it 
has  only  been  by  the  study  of  specimens  from  the  type  localities  in  the 
Mohawk  Valley  that  the  real  characters  of  the  species  have  been  identified. 
Vanuxem's  very  imperfect  description  is  as  follows : 

"  [0.  complanata]  consists  of  many  convolutions  resembling  a  single 
coil  of  cord  formed  on  a  flat  surface,  the  diameter  of  the  coil  being  usually 
about  an  inch.  From  analogy  of  formation  it  evidently  pertains  to  the 
same  genus  with  0.  levata.  It  is  more  rare  than  0.  levata,  but  is  occa- 
sionally met  with  in  the  same  localities  on  the  Mohawk." 

The  type  specimen  of  0.  complanata  appears  to  be  lost,  but  as  noted 
by  Cleland,  there  is  little  doubt  that  the  species  described  by  him  as 
Pleurotomaria  hunterensis  has  usually  been  identified  as  0.  complanata 
in  the  Mohawk  Valley.  Both  names  undoubtedly  refer  to  the  same 
species,  especially  since  the  occurrence  of  each  is  identical.  Although 
Vanuxem's  description  and  figure  are  not  sufficient  for  present-day  pur- 
poses, it  seems  best  to  recognize  his  name  on  account  of  the  generic  term 
Ophileta.  If  the  genotype  0.  complanata  should  not  be  recognized'  the 
widely  quoted  genus  Ophileta  too  would  have  to  be  dropped.  The 
synonymy  is  further  complicated  by  the  fact  that  Weller  has  based  his 
genus  Poly gy rat a  on  a  species  from  New  Jersey  apparently  closely  related 
to  Ophileta  complanata.  With  regard  to  the  numerous  other  references 
to  supposed  0.  complanata,  this  is  neither  the  time  nor  the  place  to  discuss 
them.  Only  a  monographic  faunal  study  of  the  entire  Canadian  can 
clear  up  this  complicated  subject. 

Occurrence. — BEEKMANTOWN  LIMESTONE  (Stonehenge  member). 
Vicinity  of  Hagerstown  and  Funkstown,  Maryland. 

The  type  localities  are  in  the  Mohawk  Valley  of  New  York,  Little  Falls, 
Canajoharie,  Tribes  Hill,  Ft.  Hunter,  etc.,  where  the  species  occurs  in  the 
Tribes  Hill  division  of  the  Canadian. 

Collections. — Maryland. Geological  Survey,  U.  S.  National  Museum. 
20 


304  SYSTEMATIC  PALEONTOLOGY 

OPHILETA  LEVATA  Vanuxem 
Plate  XXXI,  Figs.  18, 19 

OpMleta  levata  Vanuxem,  1842,  Nat.  Hist.  New  York,  Geol.,  vol.  iii,  p.  36, 

fig.  1. 

OpMleta  levata  Cleland,  1903,  Bull.  Amer.  Pal.,  vol.  iv,  p.  16. 
OpMleta  discus  Cleland,  1900,  Bull.  Amer.  Pal.,  vol.  iii,  p.  124  (252),  pi.  xv, 

figs.  5,  6. 

Description. — Shell  discoidal,  10  mm.  or  less  in  diameter,  consisting 
of  four  or  more  whorls  rising  into  a  slightly  elevated  spire,  and  concave 
on  the  lower  side  where  the  umbilicus  is  wide  and  shows  all  of  the  whorls. 
Margin  of  whorls  sharp  and  somewhat  elevated ;  upper  side  of  whorl  flat, 
lower  side  rounded. 

The  identification  of  the  specimens  here  referred  to  Ophileta  levata 
is  due  to  Cleland  who  by  a  comparison  of  type  specimens  of  each  has 
shown  that  his  Ophileta  discus  and  Vanuxem's  0.  levata  are  based  on  the 
same  species.  As  in  the  case  of  Ophileta  complanata,  Vanuxem's  descrip- 
tion and  figure  of  0.  levata  are  of  little  value. 

Occurrence. — BEEKMANTOWN  LIMESTONE  (Stonehenge  member). 
Vicinity  of  Hagerstown  and  Funkstown,  Maryland. 

Abundant  in  the  Tribes  Hill  limestone  of  the  Canadian  at  Canajoharie, 
Tribes  Hill,  Fort  Hunter  and  other  localities  in  the  Mohawk  Valley  of 
New  York. 

Collection. — U.  S.  National  Museum. 


Plate  XXXIII,  Figs.  1-3 ;  Plate  XXXIV,  Fig.  2 

OpMleta  compacta  Salter,  1859,  Quart.  Jour.  Geol.   Soc.  London,  vol.  xv, 

p.  378,  pi.  xiii,  fig.  12. 
OpMleta  complanata  Whitfield,  1889,  Bull.  Amer.  Mus.  Nat.  Hist.,  vol.  ii, 

p.  48,  pi.  vii,  figs.  18-25. 

Description. — Shells  discoidal,  coiled  in  the  same  plane ;  flat  or  slightly 
concave  below,  more  concave  above.  Periphery  flattened  obliquely,  the 
lower  edge  of  the  volution  being  the  largest,  and  rounded  to  the  base, 
while  the  upper  angle  is  sharply  carinate.  Upper  surface  of  each  volution 


MARYLAND  GEOLOGICAL  SURVEY  305 

obliquely  sloping  to  the  volution  within  it,  giving  the  depressed  spire. 
Aperture  trapezoidal.  Substances  of  the  shell  thick,  the  surface  trans- 
versely striated  on  the  top  and  below,  with  frequent  strongly  marked 
undulations  on  the  flattened  side  and  back  of  the  volution. 

The  above  description  is  based  upon  fairly  well  preserved  examples  of 
this  species  from  the  Beekmantown  of  the  Champlain  Valley,  described 
and  illustrated  by  Whitfield  as  Ophileta  complanata.  Typical  Ophileta 
complanata  is  quite  a  different  shell,  as  can  be  noted  by  a  comparison  of 
the  figures  on  plates  XXXI  and  XXXIIL 

Occurrence. — BEEKMANTOWN  LIMESTONE  (Cryptozoon  steeli  zone). 
Poor  casts  in  the  rock  or  in  the  form  of  natural  sections.  Hagerstown, 
etc.,  Maryland  and  various  localities  in  Pennsylvania. 

Collection. — U.  S.  National  Museum. 

Genus   EGGYLIOMPHALUS  Portlock 

ECCYLIOMPHALUS   MULTTSEPTARIUS   Cleland 

Plate  XXXI,  Figs.  20,  21;' Plate  XXXIV,  Figs.  3,  4 

Ecculiomphalus  multiseptarius  Cleland,   1900,   Bull.   Amer.    Pal.,   vol.   iii, 

p.  123  (251),  pi.  xv,  figs.  1-4. 
Ecculiomphalus   multiseptarius   Cleland,    1903,   Bull.   Amer.    Pal.,   vol.   iv, 

p.  17. 

Description. — The  shell  of  this  species  is  discoid  and  consists  of  two 
or  more  loosely  coiled,  slender  volutions  which  gradually  expand  until 
the  outer  portion  is  6  mm.  in  diameter  in  a  specimen  of  20  mm.  width. 
In  transverse  section  the  outer  coil  of  the  shell  is  subovate  and  slightly 
carinated  on  the  outer  edge. 

The  specific  name  refers  to  the  partitions  shown  in  natural  section  of 
the  shell  which  give  it  the  aspect  of  a  cephalopod,  but  the  curvature  and 
the  irregularity  of  these  partitions  will  distinguish  them  from  septa. 
Such  partitions  are  known  in  other  species  of  the  genus  and  indeed  form 
a  generic  character.  They  are  especially  well  developed  in  the  present 
species. 

Occurrence. — BEEKMANTOWN  LIMESTONE  (Stonehenge  member). 
Rare  in  both  the  lower  and  upper  divisions  of  the  Stonehenge  member 


306  SYSTEMATIC  PALEONTOLOGY 

at  several  localities  in  the  vicinity  of  Hagerstown,  Maryland.  Natural 
sections  of  this  shell  can  be  seen  in  the  lower  Stonehenge  quarries  and 
especially  in  the  fences  along  the  National  Highway,  one-fourth  to  one- 
half  mile  south  of  Funkstown,  Maryland. 

Not  uncommon  in  the  Tribes  Hill  formation  of  the  Canadian  near 
Fort  Hunter,  New  York. 

Collection. — U.  S.  National  Museum. 

ECCYLIOMPHALUS  TRENTONENSIS    (Conrad) 

Plate  L,  Figs.  19,  20 

Cyrtolites  trentonensis  Conrad,  1842,  Jour.  Acad.  Nat.   Sci.,  Philadelphia, 

vol.  viii,  p.  270,  pi.  xvii,  fig.  4. 
Cyrtolites  trentonensis  Hall,  1847,  Pal.  New  York,  vol.  i,  p.  189,  pi.  xla, 

figs.  3a-d. 
Eccyliomphalus  trentonensis  Weller,  1903,  Geol.   Surv.   New  Jersey,  Pal., 

vol.  iii,  p.  184,  pi.  xii,  figs.  20,  21. 

Description. — Shell  consisting  of  less  than  one  volution,  increasing 
gradually  in  size  from  the  apex,  coiled  in  one  plane.  Cross-section 
angularly  subovate.  Ventral  side  of  the  shell  convex  from  the  periphery 
to  the  inner  margin;  the  periphery  rather  sharply  rounded;  about  mid- 
way between  it  and  the  inner  margin,  on  the  dorsal  side  of  the  shell,  is  an 
angular,  subcarinate  ridge,  the  space  between  this  ridge  and  the  peripheral 
angulation  being  nearly  flat;  from  the  dorsal  ridge  to  the  inner  margin 
of  the  shell  the  surface  is  convex.  The  surface  is  marked  by  rather 
obscure  and  irregular  lines  of  growth,  which,  on  the  dorsal  side,  slope 
backward  to  the  dorsal  ridge,  thus  indicating  the  presence  of  an  angular 
sinus  in  the  aperture  at  that  point.  The  most  complete  specimen  observed 
has  a  length  of  about  35  mm.  around  the  periphery  of  the  shell  from  apex 
to  aperture."— Weller,  1903. 

Occurrence. — MARTINSBURG  SHALE  (Sinuites  bed).  Carlisle,  Cham- 
bersburg  and  two  miles  south  of  St.  Thomas,  Pennsylvania.  The  Lower 
Trenton  rocks  of  New  York  and  New  Jersey  likewise  have  furnished 
specimens. 

Collection. — U.  S.  National  Museum. 


307 

Family  RAPHISTOMIDAE 

Genus  RAPHISTOMA  Hall 
EAPHISTOMA  ?  OBTUSUM  Cleland 

Plate  XXXI,  Figs.  15-17 

Raphistoma  obtusa  Cleland,  1900,  Bull.  Amer.  Pal.,  vol.  iii,  p.  125   (253), 
pi.  xv,  figs.  7-9. 

Description. — Shell  averaging  10  mm.  in  width,  convex  above,  much 
compressed  and  consisting  of  three  volutions,  forming  an  apical  angle 
of  130°.  Umbilicus  about  one-third  the  shell  diameter,  with  angular 
margins.  Upper  surface  of  volutions  compressed,  outer  edge  acute,  and 
inner  edge  rounded. 

The  compressed  form,  angular  margin,  and  few  volutions  of  this  shell 
will  distinguish  it  from  associated  species. 

Occurrence. — BEEKMANTOWN  LIMESTONE  (Stonehenge  member). 
Several  localities  around  Hagerstown  and  Funkstown,  Maryland.  Tribes 
Hill  limestone  of  New  York. 

Collection. — U.  S.  National  Museum. 

EAPHISTOMA  ?  COLUMBIANUM  Weller 

Plate  XXXI,  Figs.  22,  23 

Raphistoma  columbiana  Weller,  1903,  Geol.  Surv.  New  Jersey,  Pal.,  vol.  iii, 
p.  128,  pi.  iv,  figs.  3-5. 

Description. — Shell  nearly  smooth,  consisting  of  about  three  and  one- 
half  volutions,  flat  above  and  rounded  below,  which  form  a  slightly 
elevated  spire  and  have  a  small  umbilicus  below.  Outer  edge  of  shell 
sharply  rounded  and  slightly  elevated  above.  The  outer  volution  has  a 
broad,  ill-defined  sulcus  just  below  and  paralleling  the  periphery.  The 
type  specimen  measures  13  mm.  in  diameter  and  6.5  mm.  in  height. 

Occurrence. — BEEKMANTOWN  LIMESTONE  (Stonehenge  member). 
Hagerstown,  Maryland.  The  types  are  from  the  Kittatinny  limestone 
of  New  Jersey. 

Collection. — U.  S.  National  Museum. 


308  SYSTEMATIC  PALEONTOLOGY 

Genus  RAPHISTOMINA  Ulrich  and  Scofield 
BAPHISTOMINA  LAUKENTINA  (Billings) 

Plate  XXXVI,  Figs.  6,  7 

Pleurotomaria  laurentina  Billings,  1859,  Canadian  Nat.  Geol.,  vol.  iv,  p.  354, 
fig.  6. 

Description. — Shell  25  to  50  mm.  in  diameter,  lenticular  with  depressed 
spire  consisting  of  five  or  six  Avhorls  slightly  convex  on  their  upper  sides, 
but  with  a  shallow  concave  band  just  within  their  outer  margin.  Lower 
.side  of  body  whorl  somewhat  concave  just  beneath  the  margin,  then 
moderately  convex  to  the  umbilicus  within  which  it  is  rather  narrowly 
rounded.  Umbilicus  deep  and  about  one-fourth  the  diameter  of  the 
shell.  The  cast  of  the  interior  exhibits  an  acutely  rounded  margin, 
which,  owing  to  the  concave  band  above,  appears  to  be  turned  a  little 
upward,  or  to  have  a  narrow  ridge  all  around  on  its  upper  side.  Aperture 
subrhomboidal,  somewhat  indented  by  the  adjacent  whorl. 

The  Appalachian  Valley  specimens  are  poorly  preserved,  but  agree  in 
all  essential  details  with  the  figures  of  the  Canadian  specimens  published 
by  Billings. 

Occurrence. — BEEKMANTOWN  LIMESTONE  (Ceratopea  zone).  Stouf- 
ferstown,  Pennsylvania,  and  east  of  Williamsport,  Maryland. 

Collection. — TJ.  S.  National  Museum. 

Genus  OMOSPIRA    Ulrich 
OMOSPIKA  ALEXANDKA  (Billings) 

Plate  XLIII,  Figs.  16,  17 

Murchisonia  Alexandra  Billings,   1865,   Geol.   Surv.   Canada,   Pal.   Fossils, 

vol.  I,  p.  172. 
Omospira  alexandra  Ulrich  and  Scofield,  1897,  Geol.  Minnesota,  vol.  iii,  pt.  2, 

p.  946,  pi.  Ixx,  figs.  66,  67. 

Description. — •"  Shell  rather  large,  turbinate,  acutely  conical ;  apical 
angle  from  45°  to  50° ;  whorls  about  six,  strongly  ventricose,  with  a  flat 
band  in  the  upper  third.  The  aperture  appears  to  be  large  and  ovate; 


MARYLAND  GEOLOGICAL  SURVEY  309 

the  inner  lip  is  thin  and  folded  over  so  as  to  conceal  the  minute  umbilicus. 
Surface  finely  striated.  Length  about  30  lines;  width  of  body  whorl 
15  lines. 

This  species  is  about  the  size  and  somewhat  of  the  shape  of  M.  belli- 
cincta.  The  principal  difference  is  in  the  form  of  the  upper  part  of  the 
whorl.  The  lower  two-thirds  or  three-fourths  of  the  whorl  is  nearly 
uniformly  convex,  but  the  upper  third  descends  abruptly  to  the  deep 
suture.  The  band  is  quite  flat,  and  being  situated  on  the  upper  sloping 
part,  gives  to  the  whorl  a  truncated  appearance.  The  lower  edge  of  the 
band  is  defined  by  a  small  acute  carina,  seldom  visible  in  specimens  which 
are  worn." — Billings,  1865. 

Occurrence. — CHAMBERSBURG  LIMESTONE  (Tetradium  cellulosum  bed) . 
Fort  Loudon,  Franklin  County,  Pennsylvania.  Lowville  limestone  of 
Canada  and  Kentucky. 

Collection. — U.  S.  National  Museum. 

Family  BUCANIIDAE 

Genus  BUGANIA    Hall 
BUCANIA  SULCATINA  (Emmons) 

Plate  XXXIX,  Figs.  6-8 

Bellerophon  sulcatinus  Emmons,  1842,  Geol.  Nat.  Hist.  New  York,  vol.  ii, 

p.  312,  text  fig.  4. 
Bucania  sulcatina  Hall,  1847,  Pal.  New  York,  vol.  i,  p.  32,  pi.  vi,  figs.  10,  lOa; 

pi.  xxxiii,  fig.  4d. 
Bucania  champlainensis  Whitfield,  1897,  Bull.  Amer.  Mus.  Nat.  Hist.,  vol.  ix, 

p.  181,  pi.  iv,  figs.  14-16. 
Bucania  sulcatina  Raymond,   1908,   Ann.   Carnegie  Mus.,   vol.   iv,   p.   194, 

pi.  xlix,  figs.  15-17;  pi.  1,  figs.  3,  4;  pi.  Iv,  figs.  13,  14. 

Description. — "  Shell  large,  coiled  in  one  plane,  umbilicated  on  both 
surfaces,  all  the  whorls  visible.  The  whorls  are  broad,  somewhat  angular 
at  the  sides,  the  last  whorl  moderately  expanded  at  the  mouth.  Shell  on 
the  whorls  thin,  but  on  the  lip  it  becomes  very  thick  and  sometimes  corru- 
gated. The  surface  is  ornamented  by  coarse  wavy  revolving  striae  which 
are  crossed  by  transverse  lines  of  growth. 


310  SYSTEMATIC  PALEONTOLOGY 

"  These  lines  turn  backward  in  crossing  the  middle  of  the  shell  and 
then  forward  again  on  either  side.  Along  the  center  of  the  shell  runs  a 
narrow  carina  or  slit  band  which  is  open  for  a  short  distance  on  the  last 
whorl.  The  lip  shoAvs  a  broad,  deep  notch  on  the  outer  edge,  and  at  the 
base  of  this  notch  is  a  further  slit.  On  most  specimens  this  carina  is  a 
flat  or  depressed  band,  but  on  a  few,  especially  on  young  specimens  and 
on  the  outer  whorl  of  adults,  the  carina  is. elevated." — Raymond,  1908. 

This  well-known  Chazyan  fossil  is  easily  recognized  by  the  shape  of  the 
shell  with  a  slit  band,  and  especially  by  its  characteristic  reticulate  surface 
markings. 

Occurrence. — STONES  RIVER  LIMESTONE  (Middle  division).  Examples 
have  been  collected  at  the  old  quarry  at  Chambersburg,  Pennsylvania, 
and  south  along  this  band  of  outcrop  into  Maryland.  Chazyan  of  the 
Lake  Champlain  area  and  Tennessee. 

Collections. — Maryland  Geological  Survey,  TJ.  S.  National  Museum. 

Genus  TETRANOTA  Ulrich  and  Scofleld 
TETRANOTA  OBSOLETA  Ulrich 

Plate  LV,  Figs.  22-24 

Tetranota  obsoleta  Ulrich  and  Scofield,  1897,  Geol.  Minnesota,  vol.  iii,  pt.  2, 
p.  880,  pi.  Ixv,  figs.  19-23. 

Description. — This  species  differs  from  other  members  of  the  genus, 
and  especially  from  the  genotype  Tetranota  bidorsata,  in  the  fact  that  the 
revolving  ridges  are  much  less  developed,  particularly  on  the  last  volution. 
The  central  lateral  pair  is  quite  obsolete  except  on  the  inner  volutions 
and  even  the  central  pair  merely  maintains  the  same  strength  relatively 
that  it  held  in  earlier  stages.  Interior  casts  of  the  mature  shell  exhibit 
a  broad,  comparatively  low,  and  more  or  less  distinctly  grooved  central 
ridge,  beyond  which  the  surface  is  first  shallowly  excavated  and  then 
gently  convex  to  the  lateral  boundaries  of  the  volutions  which  again  are 
not  angular  but  rounded.  The  exterior  of  the  shell  appears  the  same 
except  that  the  ridges  bordering  the  slit  band  seem  thinner  and  sharper. 


MARYLAND  GEOLOGICAL  SURVEY.  311 

Another  point  of  difference  from  T.  bidorsata  is  that  the  umbilicus  is 
smaller  and  less  abrupt  and  the  volutions  more  rounded  on  each  side  and 
therefore  elongate,  reniform  in  cross-section.  In  the  Eden  shales,  speci- 
mens of  this  species  average  20  mm.  in  height. 

Occurrence. — MARTINSBURG  SHALE  (Eden  division).  Jordans  Knob, 
one  and  one-half  miles  northeast  of  Fort  Loudon;  Tuscarora  Mountain, 
two  and  one-half  miles  southeast  of  McConnellsburg ;  and  Cowan  Gap, 
five  miles  northeast  of  McConnellsburg. 

Collection. — U.  S,  National  Museum. 

Family  CYRTOLITIDAE 

Genus  CYRTOLITINA    Ulrich 

CYRTOLITINA  NITIDULA  (Ulrich) 

Plate  L,  Figs.  17-18 

Cyrtolites  nitidulus  Ulrich,  1879,  Jour.  Cincinnati  Soc.  Nat.  Hist,  vol.  ii, 

p.  12,  pi.  vii,  figs.  7,  7a. 
Cyrtolitina  nitidula  Ulrich,  1897,  Geol.  Minnesota,  Pal.,  vol.  iii,  pt.  2,  p.  866, 

pi.  Ixii,  figs.  53-55. 

Description.—"  Shell  small,  6  to  8  mm.  in  diameter ;  volutions  about 
two,  rapidly  increasing  in  size,  the  outer  embracing  quite  a  half  of  the 
inner ;  dorsum  blunt,  thick,  flattened  in  casts ;  sides  gently  convex  to  the 
edge  of  the  umbilicus  into  which  they  descend  at  first  rather  abruptly, 
then  gently,  the  ventral  part  spreading  saddle-like  over  the  inner  volu- 
tion. Aperture  subcordate,  notched  below;  outer  lip  rather  broadly  and 
deeply  emarginated.  Umbilicus  about  3.5  mm.  wide  in  a  specimen  8  mm. 
in  diameter,  narrowly  rounded  at  the  edge.  Surface  of  casts  with  distinct, 
subregular,  retrally  curved,  transverse  striae,  averaging  about  five  in 
2  mm.  on  the  sides  and  back.  The  striae  continue  over  and  are  quite 
distinct  and  curved  on  the  flattened  dorsum  or  slit-band.  On  the  latter 
some  very  fine  revolving  lines,  about  four  in  1  mm.,  occur  on  the  sides  of 
the  volutions.  Greatest  diameter  of  a  large  specimen  8.3  mm. ;  width  of 
aperture  5.0  mm.;  height  of  same  5.0  mm."' — Ulrich,  1897. 


312  .    SYSTEMATIC  PALEONTOLOGY 

The  form  of  the  volutions,  the  slit-band,  and  the  striate,  almost 
lamellose,  surface  markings  characterize  this  interesting  shell  which  has 
hitherto  been  known  only  from  the  Trenton  rocks  of  the  Ohio  Valley. 

Occurrence. — MARTINSBURG  SHALE  (Sinuites  bed).  Chambersburg, 
Pennsylvania.  Trenton  at  Covington,  Kentucky. 

Collection. — U.  S.  National  Museum. 

Genus  MICROGERAS  Hall 
MlCEOCEEAS   INOENATUM    (Hall) 

Plate  L,  Figs.  21,  22 

Microceras  inornatus  Hall,  1845,  Amer.  Jour.   Sci.  and  Arts,  vol.   xlviii, 

p.  294. 
Cyrtolites  (Microceras)  inornatus  Meek,  1873,  Geol.  Surv.  Ohio,  Pal.,  vol.  i, 

p.  147,  pi.  xiii,  figs.  4a,  b. 
Cyrtolites  subcompressus  Meek,  1873,  Geol.  Surv.  Ohio,  Pal.,  vol.  i,  p.  147 

(under  C.  inornatus). 

Description. — Shell  minute,  the  largest  diameter  being  1.25  mm.  or 
less,  consisting  of  two  rapidly  diminishing  volutions  which  form  a  spire 
equally  depressed  on  either  side  and  obtusely  carinated  or  angular  upon 
the  back.  The  carina  is  most  conspicuous  near  the  aperture  and  gradu- 
ally becomes  obsolete.  The  aperture  is  somewhat  quadrangular  and  the 
surface  is  smooth. 

This  shell  occurs  almost  invariably  in  association  with  several  species 
of  Cyclora,  similar  minute  or  dwarfed  gastropods  of  larger  species  such 
as  Cyclonema  or  Lophospina.  In  themselves  these  shells  are  of  little  value 
as  horizon  markers  and  it  is  only  in  association  with  other  species  that 
they  are  useful. 

Waagen  supposed  the  species  of  Microceras  to  represent  "  embryonic 
volutions  of  bellerophontes,"  but  they  are  more  likely  dwarfed  varieties 
or  embryqnic  stages  of  some  carinated  genus  such  as  Cyrtolites. 

Occurrence. — MAETINSBURG  SHALE  (Sinuites  bed).  Chambersburg, 
Pennsylvania.  Mohawkian  and  Cincinnatian  rocks  of  the  Ohio  Valley, 
etc. 

Collections. — Maryland  Geological  Survey,  U.  S.  National  Museum. 


MARYLAND  GEOLOGICAL  SURVEY  313 

Family    SINUITIDAE 

Genus  SIMJITES  Koken 

SlNUITES  CANCELLATUS    (Hall) 

Plate  LV,  Pigs.  12-21;  Plate  L,  Figs.  37-39 

Bellerophon  bilobatus  Emmons  (not  Sowerby),  1842,  Geol.  New  York,  vol.  ii, 

p.  392,  fig.  6. 
Bellerophon  cancellatus  Hall,  1847,  Pal.  New  York,  vol.  i,  p.  307,  pi.  Ixxxiii, 

figs.  lOa-c. 
ProtowartMa  cancellata  Ulrich  and  Scofield,  1897,  Minnesota  Geol.  Survey, 

Pal.,  vol.  iii,  pt.  2,  p.  872,  pi.  Ixiii,  figs.  1-14. 
ProtowartMa  cancellata  Weller,  1903,  Geol.  Surv.  New  Jersey,  Pal.,  vol.  iii, 

p.  175,  pi.  xii,  figs.  3-5. 

Description.—  "  Shell  of  medium  size,  subglobose,  close  coiled,  with  no 
umbilicus  when  the  shell  is  preserved,  but  with  a  small  one  in  the  casts. 
In  immature  specimens  the  dorsum  of  the  outer  volution  is  rather  sharply 
rounded,  but  with  increasing  age  it  becomes  more  broadly  rounded,  losing 
entirely  the  obscure  carination  of  the  youngei  shells.  Sinus  shallow, 
rounded ;  the  lateral  margins  of  the  aperture  on  either  side  of  the  sinus 
regularly  and  rather  gently  convex.  Aperture  wider  than  high,  subsemi- 
circular  in  outline.  On  the  larger  internal  casts  one  or  more  rather  broad 
and  shallow,  rounded,  transverse,  wrinkle-like  depressions  are  frequently 
present  near  the  aperture  and  parallel  with  the  apertural  margin. 

"  The  dimensions  of  a  large  specimen  are :  Maximum  diameter,  21  mm. ; 
width  of  aperture,  18  mm." — Weller,  1903. 

A  wide-spread  species  of  the  United  States  and  Canada  ranging  from 
the  Trenton  to  and  through  the  Kichmond.  In  Pennsylvania  and  Mary- 
land the  species  occurs  at  practically  all  the  outcrops  of  the  fossiliferous 
Sinuites  bed  and  Eden  divisions  of  the  Martinsburg  shale. 

Occurrence. — MARTINSBURG  SHALE.  The  slopes  of  Eickard  Mountain 
in  Maryland  have  furnished  casts  of  the  species. 

Collections. — Maryland  Geological  Survey,  U.  S.  National  Museum. 


314  SYSTEMATIC  PALEONTOLOGY 

SlNUITES  GRANISTEIATUS    (Ulrich) 

Plate  LV,  Figs.  9-11 ;  Plate  L,  Figs.  40,  41 

ProtowartMa  granistriata  Ulrich,  1897,  Minnesota  Geol.  Survey,  Pal.,  vol. 
iii,  pt.  2,  p.  870,  pi.  Ixiii,  figs.  28-30. 

Description. — "  Shell  scarcely  reaching  the  medium  size,  closely  coiled, 
leaving  no  umbilicus;  center  of  dorsum  raised  into  a  low  broad  ridge, 
defined  on  each  side  by  an  obscure  wide  furrow;  with  age  the  outer 

*/  .7  o 

boundaries  of  the  latter  increase  gradually  in  distinctness,  the  back  of  the 
outer  half  of  the  last  volution  in  the  largest  specimens  presenting  a 
flattened  appearance ;  but  the  central  ridge,  though  decreasing  somewhat 
in  hight,  continues  to  the  aperture.  In  casts  of  the  interior  there  is  a 
small  umbilicus,  while  the  central  ridge  is  nearly  as  on  the  shell  itself. 
Aperture  transverse,  about  twice  as  wide  as  high,  the  width  generally 
equalling  the  hight  of  the  shell;  sinus  wide,  only  moderately  deep,  the 
margin  of  the  lobes  bending  rather  sharply  where  the  apertural  margin  is 
intersected  by  the  faintly  raised  boundaries  of  the  flattened  dorsum. 
Except  in  the  umbilical  regions  the  test  is  thin.  Out  of  nearly  30  speci- 
mens,, only  two  preserve  anything  of  the  external  layer.  These  show  that 
it  is  marked  by  fine  lines  of  growth  and  by  very  delicate  revolving  lines. 
All  of  the  other  testiferous  examples  preserve  only  the  inner  and  middle 
layers,  the  latter  appearing  in  every  case  quite  smooth.  Most  of  the 
specimens  preserve  what  may  be  called  a  fourth  layer.  This  seems  to 
have  been  deposited  by  the  inner  mantle  over  the  inner  volutions,  includ- 
ing the  smaller  half  of  the  outer,  while  on  each  side  it  extends  around  the 
callous  filling  of  the  umbilicus.  The  whole  of  this  layer  is  finely  granu- 
lose,  except  the  lateral  extensions,  and  these  are  covered  by  wavy  revolving 
striae.  Hight  of  an  average  shell,  !19  mm.;  width  of  aperture,  19  mm.; 
median  hight  of  same,  9.3  mm. ;  width  of  inner  volution,  6  mm. ;  depth 
of  sinus,  5  mm. ;  width  of  same,  about  10  mm." — Ulrich,  1897. 

This  shell  is  related  to  the  preceding  Sinuites  cancellatus,  but  the  latter 
species  has  a  deeper  sinus,  a  rounder  back  and  no  dorsal  ridge  nor  obscure 
furrows.  When  well  preserved,  the  difference  in  surface  markings  is  also 
a  distinguishing  character. 


MARYLAND  GEOLOGICAL  SURVEY  315 

The  types  are  from  the  Eden  shale  of  the  Ohio  Valley.  In  the  Appa- 
lachian Valley  the  species  is  known  from  the  corresponding  horizon  in 
southern  Pennsylvania,  the  upper  part  (Eden)  of  the  Martinsburg  shale, 
and  also  from  the  Sinuites  bed. 

Occurrence. — MARTINSBURG  SHALE.  Jordans  Knob,  one  and  one-half 
miles  northeast  of  Fort  London;  Chamber sburg ;  two  miles  south  of 
St.  Thomas,  Pennsylvania ;  Eickard  Mountain,  Maryland. 

Collection. — U.  S.  National  Museum. 

Family    TROCHONEMATIDAE 

Genus  STROPHOSTYLUS  Hall 

STROPHOSTYLUS  TEXTILIS  Ulrich  and  Scofield 

Plate  L,  Figs.  31-36 

Strophostylus  textilis  Ulrich  and  Scofield,  1897,  Minnesota  Geol.  Survey,  Pal., 
vol.  iii,  pt.  2,  p.  1064,  pi.  Ixxxii,  figs.  49-54. 

Description. — "  Shell  rather  small,  12  to  25  mm.  high,  11  to  20  mm. 
wide,  obliquely  conical;  apical  angle  60°  to  70°;  whorls,  in  casts,  three 
or  four,  in  entire  shells,  six  or  seven,  increasing  quite  regularly  in  size 
from  the  acute  apex,  almost  uijiformly  rounded,  often  with  several  widely 
separated,  deep,  oblique  constrictions;  suture  deep;  aperture  subovate, 
oblique;  inner  lip  appearing  thin  in  a  ventral  view,  but  when  a  part  of 
the  outer  wall  is  removed  it  is  seen  that  it  forms  a  moderately  thick 
columella  with  a  spiral  fold  beginning  near  the  lower  angle.  In  young 
examples  neither  the  fold  nor  a  spiral  furrow  just  above  it  is  very  distinct, 
while  in  some  cases  the  whole  inner  lip  appears  to  be  simple  and  thin  as 
in  Holopea.  Surface  beautifully  cancellated  by  subequal,  fine,  sharp, 
revolving  and  obliquely  transverse  lines,  the  network  growing  strong 
enough  on  the  last  whorl  to  be  distinctly  visible  to  the  naked  eye." — 
Ulrich  and  Scofield,  1897. 

The  graceful  form  and  beautiful  markings  of  this  shell  are  features 
which  aid  in  its  ready  recognition. 

Occurrence. — MARTINSBURG  SHALE  (Sinuites  bed).  Chambersburg, 
Pennsylvania.  Black  River  and  Trenton  of  Minnesota,  Missouri  and 
Kentucky. 

Collection. — TJ.  S.  National  Museum. 


316  SYSTEMATIC  PALEONTOLOGY 

Genus  CYCLORA    Hall 

CYCLOEA  MINUTA  Hall 

Plate  L,  Figs.  23-26 ;  Plate  LJI,  Figs.  10-12 

Cyclora  minuta  Hall,  1845,  Amer.  Jour.  Sci.  and  Arts,  vol.  xlviii,  p.  294. 
Holopea  nana  Meek,  1871,  Proc.  Acad.  Nat.  Sci.  Phila.,  p.  172. 
Cyclora  minuta  Meek,  1873,  Geol.  Surv.  Ohio,  Pal.,  vol.  i,  p.  152,  pi.  xiii, 
figs.  7a-e. 

Description. — Shell  small,  averaging  1.00  mm.  in  height,  smooth,  con- 
sisting of  about  three  volutions  which  rapidly  expand  toward  the  mouth 
and  form  a  moderately  elevated  spire.  The  upper  two  whorls  are  quite 
small  and  the  shell  is  formed  in  large  part  by  the  third  whorl.  The 
aperture  is  round  and  well  defined. 

This  interesting  minute  species  occurs  literally  by  the  million  at  certain 
Middle  and  Upper  Ordovician  horizons  where  usually  all  the  associated 
shells  are  similar  dwarfed  or  embryonic  forms.  Cyclora  minuta  possibly 
represents  the  very  young  stages  of  Cyclonema  or  Stropliostylus,  althougn 
its  black  corneous  shell  substance  is  quite  different  from  either  of  these 
genera.  Probably  a  closer  assumption  would  be  to  consider  them  as 
embryonic  forms  of  Holopea.  The  latter  genus,  however,  is  sparsely 
represented  by  individuals  in  the  rocks  in  which  Cyclora  abounds. 

Common  at  many  horizons  and  localities  of  the  Mohawkian  and  Cin- 
cinnatian  in  the  United  States  and  Canada.  In  the  Cumberland  Valley, 
however,  it  has  been  found  only  in  the  lower  portions  of  the  Martinsburg 
shale,  particularly  in  the  Sinuites  zone  at  the  base. 

Occurrence. — MARTINSBURG  SHALE  (Sinuites  and  Corynoides  beds). 
Chambersburg,  Pennsylvania;  Williamsport,  Maryland  and  Strasburg, 
Virginia. 

Collections. — Maryland  Geological  Survey,  U.  S.  National  Museum. 

CYCLORA  PARVULA  (Hall) 
Plate  L,  Figs.  28-30 

Turbo  f  parvulus  Hall,  1845,  Amer.  Jour.  Sci.  and  Arts,  vol.  xlviii,  p.  294. 
Cyclora  ?  parvula  Meek,  1893,  Geol.  Surv.  Ohio,  Pal.,  vol.  i,  p.  154. 

Description. — "  Spire  elevated,  volutions  about  four,  smooth ;  first 
whorl  angulated  upon  the  center  towards  the  aperture ;  outer  edge  of  the 


MARYLAND  GEOLOGICAL  SURVEY  317 

aperture  projecting  downwards.  Height  of  shell  1/15  of  an  inch." — 
Hall,  1845. 

Although  this  species  has  not  been  figured  heretofore  and  its  descrip- 
tion was  quite  meager,  there  is  no  difficulty  in  distinguishing  it  from 
other  forms  of  Cyclora  because  of  the  angulation  of  the  first  whorl  towards 
the  aperture.  The  other  species  of  Cyclora,  have  rounded  whorls  and  may 
represent  the  young  of  such  genera  as  Cyclonema  or  Hormotoma.  The 
angulated  whorl  of  Cyclora  parvula  would  suggest  its  relationship  to 
Lophospira  or  some  similar  genus. 

Common  in  association  with  Cyclora  minuta  Hall  in  the  Mohawkian 
and  Cincinnatian  rocks  at  Cincinnati,  Ohio,  and  many  other  localities. 

Occurrence. — MARTINSBURG  SHALE  .(Sinuites  bed).  Chambersburg, 
Pennsylvania,  and  Strasburg,  Virginia. 

Collections. — Maryland  Geological  Survey,  II.  S.  National  Museum. 

CYCLORA  HOFFMANNI  Miller 
Plate  L,  Fig.  27 

Cyclora  hoffmanni  Miller,  1874,  Cincinnati  Quart.  Jour.  Sci.,  vol.  i,  p.  313, 
fig.  33. 

Description.— Shell  minute,  the  average  length  being  about  1.50  mm., 
consisting  of  an  elongated  spire  made  up  of  five  or  six  volutions  which 
are  round  and  increase  gradually  in  size.  Whorls  quite  convex,  with  a 
deep  suture;  aperture  nearly  circular,  directed  slightly  downward;  sur- 
face smooth. 

This  neat,  elongate  little  species  is  usually  found  associated  with 
Cyclora  minuta  and  Micro  ceras  inornatum,  and  like  them  has  little 
stratigraphic  value.  In  the  Appalachians,  however,  these  species  are 
known  only  in  the  Trenton  portion  of  the  Martinsburg  shale. 

Occurrence. — MARTINSBURG  SHALE  (Sinuites  bed).  Chambersburg, 
Pennsylvania,  and  Strasburg,  Virginia. 

Collections. — Maryland  Geological  Survey,  U.  S.  National  Museum. 


318  SYSTEMATIC  PALEONTOLOGY 

•'-'.  order  OPISTHOBRANCHIA 

Suborder  PTEROPODA 

Family  HYOLITHIDAE 

Genus  HYOLITHES  Eichwald 

HYOLITHES  COMMUNIS  Billings 

Plate  XXV,  Figs.  5-8 

Hyolithes  communis  Billings,  1872,  Canadian  Nat.,  n.  s.,  vol.  vi,  p.  214. 
Hyolithes  communis  Walcott,  1886,  Bull.  U.  S.  Geol.  Surv.,  No.  30,  p.  136, 

pi.  xiv,  figs.  3,  3a-c. 
Hyolithes  communis  Walcott,  1890,  10th  Ann.  Rep.  U.  S.  Geol.  Surv.,  p.  620, 

fig.  65,  pi.  Ixxvii,  figs.  3,  3a-g. 

Description. — "  This  species  attains  a  length  of  about  18  lines,  although 
the  majority  of  the  specimens  are  from  10  to  15  lines  in  length.  The 
ventral  [dorsal]  side  is  flat  (or  only  slightly  convex)  for  about  two-thirds 
the  width,  and  then  rounded  up  to  the  sides.  The  latter  are  uniformly 
convex.  The  dorsum  [ventrum],  although  depressed  convex,  is  never 
distinctly  flattened,  as  is  the  ventral  [dorsal]  side.  The  lower  lip  projects 
forward  for  a  distance  equal  to  about  one-fourth  or  one-third  the  depth 
of  the  shell.  In  a  specimen  whose  width  is  three  lines,  the  depth  is  two 
lines  and  a  half. 

"  The  operculum  is  nearly  circular,  gently  but  irregularly  convex 
externally  and  concave  within.  The  ventral  [dorsal]  limb  is  seen  on  the 
outside  as  an  obscurely  triangular,  slightly  elevated  space ;  the  apex  of  the 
triangle  being  situated  nearly  in  the  center  of  the  operculum.  The  base  of 
the  triangle  forms  the  ventral  [dorsal]  margin.  This  limb  occupies  about 
one-third  of  the  whole  superficies  of  the  external  surface.  The  remainder, 
constituting  the  dorsal  [ventral]  limb,  is  nearly  flat,  slightly  elevated 
from  the  margin  towards  the  center.  On  each  side  of  the  apex  of  the 
ventral  [dorsal]  limb  there  is  a  slight  depression  running  from  the  nucleus 
out  to  the  edge.  On  the  inside  there  is  an  obscure  ridge  corresponding  to 
each  one  of  the  external  depressions.  It  is  most  prominent  where  it 
reaches  the  edge.  These  two  ridges  meet  at  the  center  and  divide  the 
whole  of  the  inner  surface  of  the  operculum  into  two  nearly  equal 
proportions. 


MARYLAND  GEOLOGICAL  SURVEY  319 

"  The  surface  of  the  operculum  is  concentrically  striated.  The  shell 
itself  in  some  of  the  specimens  is  covered  with  fine  longitudinal  striae, 
from  five  to  ten  in  the  width  of  a  line.  The  shell  varies  in  thickness  in 
different  individuals.  In  some  it  is  thin  and  composed  of  a  single  layer, 
but  in  others  it  is  much  thickened  by  concentric  laminae,  and  thus 
approaches  the  structure  of  a  Salterella.  There  are  also  fine  engirdling 
striae,  and  sometimes  obscure  subimbricating  rings  of  growth." — Billings, 
1872. 

The  above  description  with  the  emendation  as  to  the  ventral  and  dorsal 
sides  given  by  Walcott,  will  serve  for  the  recognition  of  the  poor  frag- 
ments found  in  the  Maryland  strata. 

Occurrence. — ANTIETAM  SANDSTONE.  Eakles  Mills,  Maryland,  and 
the  same  horizon  in  Pennsylvania. 

Collections. — Maryland  Geological  Survey,  U.  S.  National  Museum. 

Suborder  CONULARIIDA 

Family  TORELLELLIDAE  Holm 

Genus  SALTERELLA  Billings 

SALTERELLA  sp. 

Description. — Certain  layers  in  the  lower  part  of  the  Tomstown  lime- 
stone have  exhibited  molds  of  small,  hollow,  slender  shells  with  a  striated 
surface.  These  show  that  the  shell  is  composed  of  several  hollow  cones 
placed  one  within  the  other  as  in  the  genus  Salterella.  These  remains  are 
too  imperfect  for  description  or  illustration,  but  they  are  interesting  on 
account  of  their  occurrence  in  the  Tomstown  limestone  where  fossils  are 
exceedingly  scarce. 

Occurrence. — TOMSTOWN  LIMESTONE.  Several  localities  east  and 
southeast  of  Waynesboro,  Pennsylvania. 

Collection. — II.  S.  National  Museum. 


21 


320  SYSTEMATIC  PALEONTOLOGY 

Genus  COLEOLUS  Hall 
COLEOLUS  IOWENSIS  James 
Plate  XLIX,  Figs.  22,  23 
Coleolus  iowensis  James,  1890,  Amer.  Geol.,  vol.  v,  p.  355. 

Description. — This  species  has  never  been  illustrated,  but  it  has  been 
known  for  many  years  as  a  very  abundant  fossil  in  the  Maquoketa  shale 
of  Eichmond  age  in  Illinois  and  Iowa.  It  occurs  here  in  great  numbers 
associated  with  Cyclora  minuta  and  similar  small  gastropod  shells,  as  well 
as  such  minute  pelecypods  as  Ctenodonta  obliqua,  and  Clidophorus.  The 
shell  layer  is  seldom  preserved,  the  species  occurring  almost  invariably  as 
phosphatized  casts  of  the  interior.  The  surface  markings  of  the  outer 
shell  are  occasionally  preserved  as  molds  of  the  exterior  in  which  it  may  be 
noted  that  the  shell  surface  is  smooth  or  sometimes  very  minutely  annu- 
lated.  The  shell  itself  is  an  elongate,  gradually  tapering,  straight  or 
slightly  curved  cone,  15  to  20  mm.  long  and  a  millimeter  in  diameter  at 
its  widest  portion.  The  diameter  and  length  of  different  examples  of  the 
species  vary  considerably,  indeed  quite  frequently  these  fossils  occur  only 
as  broken  fragments. 

Occurrence. — MARTINSBUEG  SHALE  (Sinuites  bed).  Chambersburg, 
Pennsylvania. 

Abundant  in  the  Mohawkian  and  Cincinnatian  rocks  of  Iowa,  Illinois, 
and  many  other  states,  the  types  coming  from  the  Maquoketa  shale  division 
of  the  Richmond  group  of  Iowa. 

Collections. — Maryland  Geological  Survey,  U.  S.  National  Museum. 

Family   CONULARIIDAE 

Genus  GONULARIA    Miller 
CONULAHIA  TKENTONENSIS  Hall 

Plate  L,  Fig.  42 

Conularia  trentonensis  Hall,  1847,  Nat.  Hist.  New  York,  Pal.,  vol.  i,  p.  222, 

pi.  lix,  figs.  4a-f. 
Conularia  trentonensis  Weller,  1903,  Geol.  Surv.  New  Jersey,  Pal.,  vol.  iii, 

p.  188,  pi.  iii,  figs.  7,  £ . 

Description. — "  Shell  of  medium  size,  pyramidal  in  form,  quadrangular 
in  cross-section,  the  sides  diverging  from  the  apex  at  an  angle  of  about 


MARYLAND  GEOLOGICAL  SURVEY  321 

25°.  The  sides  slightly  convex,  the  angles  furrowed.  Each  side  marked 
by  a  series  of  angular,  transverse  costae,  which  are  directed  obliquely 
forward  toward  the  aperture  from  each  lateral  margin  forming  a  rounded 
angle  of  about  130°  at  the  median  line;  from  two  to  four  of  these  costae 
occupy  the  space  of  1  mm.,  being  closer  together  and  finer  near  the  apex 
of  the  shell  and  becoming  progressively  coarser  towards  the  aperture. 
The  furrows  between  the  costae  are  wider  than  the  ridges,  rounded  in  the 
bottom,  and  are  crossed  at  right  angles  by  fine  raised  bars  joining  adjacent 
costae,  which  are  somewhat  closer  together  than  the  costae  themselves  and 
not  quite  as  high. 

"  The  dimensions  of  a  specimen  which  is  somewhat  incomplete  at  the 
apex  are :  Length,  38  mm. ;  diameter  at  aperture,  18  mm." — Weller,  1903. 

Occurrence. — MARTINSBURG  SHALE  (Sinuites  bed).  Five  miles  south- 
west of  Chambersburg,  Pennsylvania,  and  at  Strasburg,  Virginia.  Treii- 
ton  limestone  of  New  York. 

Collection. — U.  S.  National  Museum. 


CLASS  CEPHALOPODA 
subclass  TETRABRANCHIATA 

Order  NAUTILOIDEA         ;,;'., 4  J:S 
Suborder    HOLOCHOANITES 
Family  ENDOCERATIDAE 
Genus  CAMEROGERAS  Conrad 

CAMEROCERAS  sp. 
Plate  XXXVII,  Fig.  10 

Description. — The  thin  slabs  of  Frederick  limestone  not  infrequently 
exhibit  subcylindrical  bodies  now  composed  of  crystalline  matter,  which 
are  supposed  to  represent  the  endosiphuncle  of  some  species  of  Carrier o- 
ceras.  With  no  other  evidence  it  is  impossible  to  identify  the  species  of 
this  cephalopod. 


32'2  SYSTEMATIC  PALEONTOLOGY 

Occurrence. — FREDERICK  LIMESTONE.  Frederick,  Maryland,  and 
neighboring  localities. 

Collection. — TJ.  S.  National  Museum. 

Suborder  ORTHOCHOANITES 
Family   ORTHOCERATIDAE 

Genus  ORTHOGERAS   Breynius 

ORTHOCERAS  PRIMIGENIUM  Vanuxem 

Plate  XXXII,  Fig.  5 

Orthoceras  primigenium  Vanuxem,  1842,  Geol.  New  York,  3d  Dist.,  p.  36, 

fig.  4. 
Orthoceras  primigenium  Whitfield,  1889,  Bull.  Amer.  Mus.  Nat.  Hist,  vol.  ii, 

No.  2,  p.  56,  pi.  x,  fig.  1. 
Orthoceras  primigenium  Cleland,  1903,  Bull.  Amer.  Pal.,  vol.  iv,  p.  14,  pi.  iii, 

figs.  8,  9. 

Description. — In  spite  of  15  or  more  references  to  this  cephalopod,  the 
species  cannot  yet  be  said  to  have  been  sufficiently  described  for  accurate 
determination.  Really  this  name  has  been  employed  for  any  gradually 
tapering,  straight  cephalopod  of  the  Canadian  in  which  the  septa  are  thin, 
deeply  concave,  and  closely  arranged.  In  the  present  case  the  same 
procedure  has  been  followed,  for  the  identification  of  this  species  in  Mary- 
land has  been  based  upon  longitudinal  sections  in  the  rock  showing  no 
other  characters  than  those  just  mentioned.  However,  it  is  believed  that 
this  identification  will  be  found  correct  when  specimens  from  the  New 
York  type  localities  are  restudied,  since  Vanuxem's  type  came  from  the 
Tribes  Hill  limestone  and  the  Maryland  examples  are  from  the  corre- 
sponding formation  in  that  state. 

Occurrence. — BEEKMANTOWN  LIMESTONE  (Stonehenge  member). 
Hagerstown,  Maryland,  and  vicinity. 

Collections. — Maryland  Geological  Survey,  U.  S.  National  Museum. 


MARYLANP  GEOLOGICAL  SURVEY  323 

ORTHOCEKAS  ARCUOLIRATUM  Hall 
Plate  XLVIII,  Fig.  22 

Orthoceras  arcuoliratum  Hall,  1847,  Pal.  New  York,  vol.  i,  p.  198,  pi.  xlii, 
figs.  7a-c. 

Description. — "  Slender,  very  gradually  tapering  to  an  acute  point ; 
surface  marked  by  strong  and  extremely  arching  or  undulating  annula- 
tions,  and  obscurely,  by  fine  longitudinal  striae;  annulations  about 
equalling  the  spaces  between  them ;  outer  chamber  and  aperture  unknown  ; 
section  circular;  siphuncle  central. 

"  The  distinguishing  features  of  this  species  are  its  slender  form  and 
extremely  arched  annulations,  which,  in  half  the  circumference,  ascend 
twice  the  width  of  the  space  between  each  annulation.  All  the  other 
annulated  species  have  the  ridges  less  arched  upon  the  back." — Hall,  1847. 

Occurrence. — CHAMBERSBURG  LIMESTONE  (Greencastle  bed).  Green- 
castle,  Pennsylvania.  Trenton  limestone  of  New  York. 

Collection. — TJ.  S.  National  Museum. 

ORTHOCERAS  JUNCEUM  Hall 
Plate  LI,  Figs.  4-7 

Orthoceras  juncevm  Hall,  1847,  Pal.  New  York,  vol.  i,  p.  204,  pi.  xlvii, 

figs.  3a-f. 
Orthoceras  junceum  Clarke,  1897,  Minnesota  Geol.  and  Nat.  Hist.  Surv.,  Pal., 

vol.  iii,  pt.  2,  p.  790. 

Description. — "  Slender,  tereta-cylindrical,  tapering  very  gradually ; 
septa  thin,  distant  from  one-fourth  to  one-third  the  diameter;  outer 
chamber  deep;  siphuncle  small,  central;  section  circular;  surface  finely 
striated  transversely,  but  without  longitudinal  striae." — Hall,  1847. 

This  rather  frequently  quoted  species  has  received  no  further  study 
since  Hall's  original  description  in  1847  and  it  is  probable  that  many 
misidentifications  of  it  have  been  made.  However,  fragments  of  an 
Orthoceras  from  the  basal  Martinsburg  shale  of  southern  Pennsylvania 
agree  so  well  with  typical  specimens  of  0.  junceum  from  the  type  locality 
that  it  is  believed  the  present  identification  is  correct. 

Occurrence. — MARTINSBURG  SHALE  (Sinuites  bed).  Chambersburg, 
Pennsylvania.  Trenton  limestone  of  New  York. 

Collection. — U.  S.  National  Museum. 


824  SYSTEMATIC  PALEONTOLOGY 

ORTHOCEKAS  TEANSVEESUM  Miller 
Plate  LV,  Fig.  27 

Orthoceras  transversum  Miller,  1875,  Cincinnati  Quart.  Jour.  Sci.,  vol.  ii, 

p.  129. 
Orthoceras  transversum  Miller,  1889,  North.  Amer.  Geol.  Pal.,  p.  452,  text 

fig.  755. 

Description. — "Shell  medium  size,  rather  rapidly  enlarging;  septa 
strongly  arched  and  distant  about  one-fourth  or  one-fifth  the  diameter 
of  the  shell ;  siphuncle  excentric,  its  form  not  observed ;  outer  shell  thin 
and  marked  by  strong  transverse  lines,  distant  from  l-100th  to  4-100ths  of 
an  inch  in  a  specimen  having  a  diameter  at  the  large  end  of  three-fourths 
of  an  inch.  The  distance  between  these  lines  seems  to  increase  as  the 
diameter  of  the  shell  increases,  but  their  distance  apart  is  not  uniform  in 
different  specimens  of  the  same  size.  About  four  or  five  of  these  trans- 
verse lines  will  mark  the  distance  between  the  septa,  though  they  do  not 
seem  to  have  any  connection  with  the  arrangement  of  the  latter" — 
Miller,  1875. 

The  well-marked  transverse  lines  of  this  species  cause  its  recognition 
to  be  quite  easy. 

Occurrence. — MAETINSBUEG  SHALE  (Eden  division).  Jordans  Knob, 
one  and  one-half  miles  northeast  of  Fort  Loudon,  Pennsylvania;  and 
Eickard  Mountain,  Washington  County,  Maryland.  Eden  shale  at  Cin- 
cinnati, Ohio. 

Collection. — U.  S.  National  Museum. 

OETHOCERAS  LAMELLOSUM  Hall 
Plate  LVIII,  Figs.  5,  G 

Orthoceras  lamellosum  Hall,  1847,  Pal.  New  York,  vol.  i,  p.  312,  pi.  Ixxxvi, 
figs.  2a-e. 

Description. — Shell  slender  and  gradually  tapering ;  septa  distant  from 
each  other  one-fifth  to  one-fourth  of  an  inch  and  having  a  convexity  about 
equal  to  their  distance  apart;  siphuncle  slightly  excentric;  surface 
apparently  lamellose  or  subimbricate. 


MARYLAND  GEOLOGICAL  SURVEY  325 

This  seems  to  be  a  well-defined  species  since  the  specimens  from 
southern  Pennsylvania  show  no  apparent  deviation  from  Hall's  figures. 
Unfortunately  these  specimens  are  no  better  preserved  than  the  types 
and  it  is  impossible  to  add  anything  to  the  above  description  except  to 
record  the  occurrence  in  new  localities. 

Occurrence. — MARTINSBURG  SHALE  (Fairview  division).  Tuscarora 
Mountain,  one  and  one-half  miles  east  of  McConnellsburg,  Pennsylvania. 
Pulaski  shale  of  New  York. 

Collection. — U.  S.  National  Museum. 

Family  CYCLOCERATIDAE 

Genus  SPYROGERAS  Hyatt 

SPYROCERAS  B'ILINEATUM  (Hall) 

Plate  LI,  Figs.  1-3 

Orthoceras   Ulineatum  Hall,   1847,  Pal.   New  York,  vol.   i,  p.   35,  pi.  vii, 

figs.  4,  4a. 
Orthoceras  bilineatum  Clarke,  1897,  Geol.  Minnesota,  vol.  iii,  pt.  2,  p.  786, 

pi.  xlvii,  figs.  20,  21;  pi.  liv,  figs.  6,  7. 

Description. — Shell  comparatively  small,  gradually  expanding,  sub- 
circular  in  cross-section.  Surface  smooth  over  the  apical  region;  con- 
centric annulations  then  develop,  very  obscure  at  first,  but  increasing  in 
strength,  until  they  become  strong,  oblique,  or  undulating  ridges  which 
are  broad  and  most  conspicuous  near  the  aperture.  Like  these  annula- 
tions the  interspaces,  which  are  somewhat  wider,  also  become  broader 
toward  the  body-chamber.  An  average  complete  shell  probably  has  a 
length  of  about  150  mm.  with  an  apertural  diameter  of  not  more  than 
20  mm. 

Surface  ornamented  by  coarse  and  fine  vertical,  elevated  lines,  crossed 
by  extremely  fine  horizontal  lines.  Slight  nodes  or  projections  mark-  the 
crossing  of  the  two  sets  of  lines.  The  smooth  portion  of  the  shell  near 
the  apex  exhibits  the  vertical  lines  in  two  simple  series.  With  growth 
the  lines  increase  in  number  and  the  alternation  in  size  of  the  striae 
becomes  less  pronounced.  The  horizontal  striae  are  quite  delicate  and 
often  not  visible  at  all. 


326  SYSTEMATIC  PALEONTOLOGY 

The  sipho  is  small  and  nearly  central.  The  septa  are  rather  shallow, 
the  sutures  transverse,  averaging  2.50  mm.  apart  and  with  no  definite 
relation  to  the  annulations.  The  latter  sometimes  being  oblique  are 
crossed  by  the  sutures  which,  however,  may  occur  within  a  furrow. 

Occurrence. — MAETINSBURG  SHALE  (Sinuites  bed).  Chambersburg, 
Pennsylvania.  Black  River  and  Trenton  of  New  York  and  Canada. 

Collection. — U.  S.  National  Museum. 

Family  TROCHOLITIDAE 

Genus  TROGHOLITES  Conrad 
TKOCHOLITES  INTEKNISTRIATUS  (Whitfield) 

Plate  XXXV,  Fig.  14 

Lituites  internistriatus  Whitfield,  1886,  Bull.  Amer.  Mus.  Nat.  Hist,  vol.  i, 

p.  332,  pi.  xxix,  figs.  5-8. 
Trocholites  internistriatus  Ruedemann,  1906,  Bull.  New  York  State  Mus., 

90,  p.  479,  pi.  xxiv,  fig.  2,  text  fig.  38. 

Description. — Shell  of  rather  small  size,  being  about  50  mm.  in  diam- 
eter, and  consisting  of  between  two  and  three  volutions.  Volutions  very 
slightly  compressed  laterally,  but  nearly  circular  in  general  outline,  with 
a  rounded  dorsal  margin.  Outer  surface  of  volutions  obliquely  annulated 
with  the  annulations  best  developed  on  the  sides  and  rounded  on  the 
surface;  in  each  case  separated  by  concave  interspaces  of  equal  width. 
The  annulations  are  directed  strongly  backward  from  the  suture  on  the 
side  of  the  shell,  where  they  gradually  die  out  and  then  become  obsolete 
or  nearly  so  on  the  dorsum.  Shell  substance  thick,  the  surface  on  the 
undulations  and  between  marked  by  strong,  almost  lamellose  striae, 
following  the  direction  of  the  undulations  on  the  sides  of  the  shell,  forming 
a  deep  retral  sinus  on  the  dorsum  indicating  a  deep  sinus  in  the  dorsal 
lip  of  the  aperture.  Interior  of  the  shell  as  indicated  in  exfoliated  speci- 
mens marked  throughout  by  very  fine,  transverse,  thread-like  striae, 
directed  almost  across  the  tube  and  numbering  about  30  in  the  space  of 
2.5  mm.  Septa  about  2.5  mm.  apart  near  the  base  of  the  outer  chamber 


MARYLAND  GEOLOGICAL  SURVEY  327 

and  apparently  rather  deeply  concave.  Siphon  near  the  inner  margin 
of  the  tube  and  comparatively  large. 

The  few  examples  of  this  fine  cephalopod  discovered  in  Maryland  do 
not  preserve  all  the  surface  features  mentioned  above,  but  they  agree  in 
size  and  general  outline. 

Occurrence. — BEEKMANTOWN  LIMESTONE  (Turritoma  zone).  Stouf- 
ferstown,  Pennsylvania,  and  east  of  Huyett,  Maryland.  Fort  Cassin, 
Vermont. 

Collection. — U.  S.  National  Museum. 

TROCHOHTES  AMMONIUS  Conrad 

Plate  L,  Fig.  43 

Trocholites  ammonius  Conrad,  1838,  2d  Ann.  Kept.  New  York  Geol.  Surv., 

p.  119. 
Trocholites  ammonius  Hall,  1847,  Pal.  New  York,  vol.  i,  p.  192,  pi.  xlA, 

figs.  4a-k. 

Description. — "  Discoidal ;  volutions  in  the  same  plane,  about  four, 
rounded,  slightly  concave  on  the  ventral  side,  gradually  enlarging  in  size 
towards  the  aperture,  which  is  slightly  expanded;  surface  marked  by 
lamellose  irregular  and  oblique  transverse  striae  or  ridges,  between  and 
upon  which  are  finer  lamellose  striae,  covering  the  outer  surface,  and 
giving  it  a  peculiar  textural  or  netted  appearance ;  striae  meeting  in  an 
arch  upon  the  back ;  septa  direct,  or  slightly  undulated  on  the  dorsal  side ; 
outer  chamber  large;  siphuncle  ventral." — Hall,  1847. 

Only  a  small  and  imperfect  example  of  this  beautiful  coiled  cephalopod 
has  been  noted  in  the  Trenton  fauna  at  the  base  of  the  Martinsburg  shale. 
So  far  as  it  goes  this  specimen  agrees  with  the  well-known  Trocholites 
ammonius  of  the  New  York  Trenton. 

Occurrence. — MARTINSBURG  SHALE  (Sinuites  bed).  Chambersburg, 
Pennsylvania.  Trenton  limestone  of  New  York  and  Kentucky. 

Collection. — U.  S.  National  Museum. 


328  SYSTEMATIC  PALEONTOLOGY 

Suborder  CYRTOCHOANITES 
Family  ACTINOCERATIDAE 

Genus  GONIOCERAS  Hall 

GONIOCEKAS  CHAZIENSE  Euedemann 

Plate  XLI,  Fig.  19 

Gonioceras  chaziense  Ruedemann,  1906,  New  York  State  Mus.   Bull.,  90, 
p.  494,  pi.  xxxvi,  figs.  3,  4. 

Description,. — "  The  natural  section  exposes  the  septa,  which  are  closely 
arranged,  there  being  10  of  them  counted  within  the  space  of  20  mm.; 
each  septum  rises  within  the  body  of  the  shell  to  about  the  height  of  five 
cameras,  forming  broad  and  low  saddles  in  the  lateral  flanges,  and  becom- 
ing slightly  deflected  backward  towards  the  outer  margin  of  the  flanges. 
Their  central  portions  are  much  thickened  by  secondary  deposits.  The 
outer  conch,  which  according  to  Hall  is  also  in  the  other  species  of 
Gonioceras  excessively  thin,  is  not  preserved;  the  greatest  width  of  the 
phragmocone,  as  indicated  by  the  septa,  is  a  little  over  70  mm.  The 
phragmocoue  appears  to  have  been  at  least  as  rapidly  expanding  as  that 
of  G.  anceps.  The  siphuncle  is  very  large  (its  diameter  7  mm.),  strongly 
nummuloidal,  filled  with  organic  deposits  which  leave  open  but  a  narrow 
endosiphotube.  From  the  latter  radiate  horizontal  tubuli  as  in  the  other 
congeners.  We  have  not  been  able  to  ascertain  the  transverse  section  of 
the  conch  and  the  surface  is  unknown." — Ruedemann,  1906. 

Occurrence. — CHAMBERSBURG  LIMESTONE  ( Caryocystites  bed).  Fort 
Loudon,  Franklin  County,  Pennsylvania.  Middle  Chazyan  of  New  York. 

Collection. — U.  S.  National  Museum. 

Family    OOCERATIDAE 

Genus  OOGERAS  Hyatt 

OOCERAS  KIRBYI  (Whitfield) 

Plate  XXXII,  Figs.  19,  20 

Cyrtoceras  kirbyi  Whitfield,  1889,  Bull.  Amer.  Mus.  Nat.  Hist,  vol.  ii,  p.  57, 

pi.  x,  figs.  4-7. 
Cyrtoceras  kirbyi  ?  Cleland,  1900,  Bull.  Amer.  Pal.,  vol.  iii,  p.  131   (259), 

pi.  xvii,  figs.  3,  4. 


MARYLAND  GEOLOGICAL  SURVEY  329 

Description. — Shell  strongly  curved  and  laterally  compressed,  increas- 
ing moderately  in  dimension  with  the  length.  Cross-section  ovate,  some- 
what more  than  three-fifths  as  wide  as  long,  with  the  widest  part  within 
the  median  line  and  the  narrowest  at  the  dorsmn,  which  is  narrowly 
rounded.  Septa  deeply  concave,  somewhat  numerous  and  closely  spaced, 
12  of  the  chambers  near  the  outer  part  on  the  dorsal  edge  occurring  in 
25  mm.  Siphon  small  and  in  contact  with  the  shell  at  the  dorsal  margin. 
Living  chamber  comparatively  long  and  apparently  not  constricted  near 
the  aperture.  Surface  of  the  shell  without  ornamentation  and  moderately 
thick. 

Occurrence. — BEEKMANTOWN  LIMESTONE  (Stonehenge  member). 
South  of  Funkstown,  Maryland.  Tribes  Hill  limestone  of  New  York. 

Collection. — U.  S.  National  Museum. 

Genus  GYRTOGERAS  Goldfuss 

CYRTOCERAS  GRACILE  Cleland 

Plate  XXXII,  Figs.  3,  4 

Cyrtoceras  sp.   Cleland,   1900,   Bull.   Amer.   Pal.,   vol.   iii,   p.   19,   pi.   xvii, 

figs.  5,  6. 
Cyrtoceras  gracilis  Cleland,  1903,  Bull.  Amer.  Pal.,  vol.  iv,  p.  13,  pi.  iii, 

fig.  11. 
Cyrtoceras  sp.  Weller,  1903,  Pal.  New  Jersey,  vol.  iii,  p.  131,  pi.  v,  figs.  7,  8. 

Description. — Shell  small,  12  mm.  long  and  8  mm.  in  diameter,  slender, 
arcuate,  oval  in  transverse  section.  Siphuncle  small  and  placed  near  the 
ventral  edge.  Septa  smooth,  slightly  concave,  close  together,  with  five 
to  six  occurring  in  4  mm. 

The  shape  and  small  size  of  this  cephalopod  and  the  closely  arranged 
septa  will  distinguish  it  from  other  Canadian  species. 

The  species  was  based  upon  specimens  from  the  Tribes  Hill  limestone 
at  Fort  Hunter,  Tribes  Hill,  and  Canajoharie,  New  York.  The  same  or  a 
very  similar  species  occurs  in  the  Canadian  portion  of  the  Kittatinny 
limestone  at  Columbia,  New  Jersey. 

In  Maryland,  natural  longitudinal  and  cross-sections  of  apparently  the 
same  species  have  been  noted  on  the  weathered  surface  of  the  lower  Stone- 
henge limestone. 


330  SYSTEMATIC  PALEONTOLOGY 

Occurrence. — BEEKMANTOWN     LIMESTONE      (Stonehenge     member). 
One-half  mile  south  of  Funkstown,  and  near  Hagerstown. 
Collection. — U.  S.  National  Museum. 

CYRTOCERAS  BEEKMANENSE  Whittle]  d 
Plate  XXXII,  Figs.  1,  2 

Cyrtoceras  beekmanensis  Whitfield,  1889,  Bull.  Amer.  Mus.  Nat.  Hist.,  vol.  ii, 
p.  57,  pi.  x,  figs.  2,  3. 

Description. — Shell  as  usually  observed,  from  75  to  100  mm.  in  length 
and  less  than  25  mm.  wide,  little  curved,  the  amount  of  curvature  not 
amounting  to  more  than  3  mm.  in  a  length  of  75  mm.;  laterally  com- 
pressed so  that  the  lateral  diameter  is  somewhat  less  than  the  dorso- 
ventral;  slightly  oval  in  cross-section.  Septa  numerous,  14  chambers 
occurring  in  25  mm.,  little  curved  and  of  shallow  depth.  Outer  chamber 
of  shell  long.  Siphon  unknown.  Surface  of  shell  apparently  smooth. 

Occurrence. — BEEKMANTOWN  LIMESTONE  (Stonehenge  member). 
National  Highway,  one-half  mile  south  of  Funkstown,  Maryland. 

Collection. — U.  S.  National  Museum. 

CYRTOCERAS  CAMURUM  Hall 
Plate  XLVIII,  Fig.  21 

Crytoceras  camurum  Hall,  1847,  Pal.  New  York,  vol.  i,  p.  196,  pi.  xlii,  fig.  6. 
Cyrtoceras  camurum  Clarke,  1897,  Geol.  Minnesota,  3,  pt.  2,  p.  805,  pi.  Ix, 
figs.  5,  6. 

Description. — Fragments  of  a  curved  cephalopod  occurring  in  the 
strata  just  above  the  typical  Christiania  bed  in  the  vicinity  of  Green- 
castle,  Pennsylvania,  are  so  similar  to  the  New  York  lower  Trenton 
species  described  as  Cyrtoceras  camurum  by  Hall  that  they  are  believed 
to  be  the  same.  In  neither  area  have  complete  specimens  been  found,  so 
that  it  is  still  impossible  to  give  a  full  description  of  the  species. 

Occurrence. — CHAMBERSBURG  LIMESTONE  (Greencastle  bed).  Green- 
castle,  Pennsylvania.  The  type  locality  is  the  Trenton  limestone  at 
Middleville,  New  York,  but  this  species  has  also  been  identified  in  the 
Black  Eiver  rocks  of  Wisconsin. 

Collection. — U.  S.  National  Museum. 


MARYLAND  GEOLOGICAL  SURVEY  331 

Genus  CYRTOGERINA  Billings 
CYRTOCERINA  MERCURIUS  Billings 

Plate  XXXV,  Fig.  13 

Cyrtocerina  mercurius  Billings,  1865,  Pal.  Foss.,  vol.  i,  Geol.  Surv.  Canada, 
p.  194,  text  fig.  179. 

Description. — Shell  short,  strongly  curved  and  tapering  abruptly; 
elliptical  in  section,  the  dorso-ventral  diameter  being  one-third  or  one- 
fourth  greater  than  the  lateral.  Measured  on  the  surface  of  the  ventral 
side  near  the  living  chamber  the  septa  are  about  1  mm.  apart,  but  on  the 
dorsal  side  near  the  apex  they  are  probably  closer  together.  Siphuncle 
in  contact  with  the  shell  on  its  dorsal  side. 

The  dorsal  position  of  the  siphuncle,  the  close  arrangement  of  the  septa, 
and  the  strongly  curved,  abruptly  tapering  features  are  characters  to  aid 
in  the  recognition  of  this  shell,  although  the  species  cannot  be  considered 
to  be  fully  described  as  yet. 

Occurrence. — BEEKMANTOWN  LIMESTONE  (Turritoma  zone).  Stouf- 
ferstown,  Pennsylvania,  and  east  of  Huyett,  Maryland. 

Collection. — U.  S.  National  Museum. 

Family    ONCOCERATIDAE 

Genus  CYCLOSTOMIGERAS  Hyatt 

CYCLOSTOMICERAS  CASSINENSE  (Whitfield)  ? 

Plate  XXXII,  Figs.  6,  7 

Gomphoceras  cassinense  Whitfield,  1886,  Bull.  Amer.  Mus.  Nat.  Hist,  vol.  i, 

p.  322,  pi.  xxix,  figs.  1-3. 
Cyclostomiceras  cassinense  Ruedemann,  1906,  New  York  State  Mus.  Bull., 

No.  90,  p.  50,  fig.  56;  pi.  xxxvii,  figs.  1-3;  pi.  xxxviii,  figs.  5,  6. 

Description. — This  species  has  been  carefully  described  by  Euedemann 
to  whose  work  of  1906  the  student  is  referred  for  details  and  illustrations. 
The  entire  shell  attains  a  size  of  about  100  mm.  and  a  greatest  width  of 
40  mm.  The  rate  of  growth  is  quite  rapid,  the  living  chamber  is  large, 
forming  nearly  half  of  the  shell,  the  septa  are  shallow,  and  the  siphuncle 
is  large.  Sections  in  the  rock  seen  at  several  Maryland  outcrops  exhibit 
a  cephalopod  with  the  same  rate  of  growth  and  other  characters  just 


332  SYSTEMATIC  PALEONTOLOGY 

mentioned,  but  better  material  is  necessary  before  the  determination  can 
be  made  with  certainty. 

Occurrence. — BEEKMANTOWN  LIMESTONE  ( Stonehenge  member). 
Near  Funkstown,  Maryland.  Cassin  beds  at  Fort  Cassin,  Vermont. 

Collection. — U.  S.  National  Museum. 

:    ARTHROPODA 

CLASS  CRUSTACEA 
subclass  TRILOBITA 

Order  HYPOPARIA 

Family  HARPEDIDAE 

Genus  EOHARPES   Raymond 

EOHAEPES  OTTAWAENSIS   (Billings) 

Plate  LI,  Fig.  11 

Harpes  ottawaensis  Billings,  1865,  Pal.  Foss.,  vol.  i,  Geol.  Surv.  Canada, 

p.  182,  text  fig.  165. 
Harpina  ottawaensis  Weller,  1903,  Geol.  Surv.  New  Jersey,  Pal.,  vol.  iii, 

p.  191,  pi.  xiv,  figs.  1,  2. 
Harpina  ottawaensis  Raymond,  1905,  Annals  Carnegie  Mus.,  vol.  iii,  p.  331, 

pi.  x,  fig.  2. 
Eoharpes  ottawaensis  Ruedemann,  1912,  New  York  State  Mus.,  Bull.  No.  162, 

p.  116,  pi.  ix,  fig.  1. 

Description. — "  Head  strongly  convex,  with  a  wide,  punctured  border 
which  extends  backward  to  about  the  thirteenth  segment  of  the  thorax. 
If  a  line  be  drawn  across  touching  the  posterior  edge  of  the  neck  seg- 
ment, the  contour  in  front  of  that  line  is  nearly  a  perfect  semicircle. 
Glabella  regularly  conical,  its  length  about  five-ninths  that  of  the  head; 
posterior  furrows  distinct,  entering  at  about  one-half  the  distance  from 
the  ocular  ridge  to  the  posterior  margin  of  the  neck  segment,  thence 
running  obliquely  inward  and  backwards  at  an  angle  of  about  45°, 
apparently  not  quite  one-third  the  width;  two  anterior  furrows  on  each 
side,  represented  by  obscure  pits;  neck  furrow  narrow;  neck  segment 
convex,  strongly  elevated  on  the  fixed  cheeks.  The  eyes  (ocelli)  are 


MARYLAND  GEOLOGICAL  SURVEY  333 

small  and  situated  on  a  line  drawn  across  the  glabella  at  the  anterior 
fourth;  ocular  ridge  well  denned,  smooth,  prolonged,  with  a  backward 
curve  outside  of  the  eye.  Thorax  a  little  more  than  half  the  width  of  the 
head;  the  axis  strongly  convex  and  gradually  tapering  backwards;  side 
lobes  flat;  plurae  with  a  wide  groove  along  the  middle,  a  small  portion  of 
their  outer  extremities  turned  backward.  Surface  of  thorax,  glabella  and 
a  subrenif orm  space  on  each  side  of  the  base  of  the  glabella  smooth ;  the 
border  with  circular  punctures  about  0.2  mm.  in  width;  the  punctures 
large  and  more  distant  at  the  inner  edge  of  the  border;  on  the  elevated 
part  of  the  cheeks  they  have  a  subreticulated  arrangement." — Billings, 
1865. 

This  splendid  species  of  which  a  nearly  complete  example  has  been 
described  as  above  by  Billings,  is  represented  in  the  Trenton  fauna  at  the 
base  of  the  Martinsburg  shale  by  fragments  only,  which,  however,  agree 
fairly  well  with  the  corresponding  parts"  of  the  specimen  figured  by 
Billings  and  here  reproduced  on  pi.  LI. 

Occurrence. — MARTINSBURG  SHALE  (Sinuites  bed).  Chambersburg, 
Pennsylvania.  Trenton  limestone  of  Ontario,  New  York  and  Minnesota. 

Collection. — TJ.  S.  National  Museum. 

Family  TRINUCLEIDAE 

Genus  GRYPTOLITHUS  Green 

CRYPTOLITHUS  BELLULUS  (Ulrich) 

Plate  LVI,  Figs.  5,  6 

Trlnucleus  bellulus  Ulrich,  1878,  Jour.  Cincinnati  Soc.  Nat.  Hist.,  vol.  i, 
p.  99,  pi.  iv,  fig.  15. 

Description. — "  Body  small,  nearly  flat,  and  symmetrical.  Cephalic 
shield  about  three  times  as  wide  as  long,  subquadrate,  with  a  distinct 
thoracic  ring  at  the  base,  which  is  straight,  with  the  posterior  angles 
acutely  angular  or  slightly  rounded,  and  without  any  long  spines ;  glabella 
prominent,  pyrif orm  and  produced  posteriorly,  into  a  long  spine,  reaching 
to  the  pygidium ;  cheeks  not  as  prominent  as  the  glabella,  triangular,  and 
finely  punctate;  marginal  fillet  wide,  marked  in  front  by  from  three  to 


334  SYSTEMATIC  PALEONTOLOGY 

four  rows  of  deep,  rounded  pores  or  punctures;  the  rows  increase  by  im- 
plantation as  they  approach  the  posterior  lateral  margins,  where  they 
number  from  six  to  seven. 

"  The  thorax  consists  of  six  articulations ;  axial  lobe  depressed,  convex, 
narrow,  and  carrying  on  each  side  between  the  segments  two  rows  of 
minute  punctures ;  lateral  lobes  flat,  and  three  times  as  wide  as  the  central 
lobe ;  pleura  straight,  and  furrowed  on  the  outer  half. 

"  Pygidium  small,  acutely  semi -elliptic,  being  about  four  times  as  wide 
as  long,  and  broadly  rounded  in  outline  behind,  with  a  raised  and  thick- 
ened margin ;  axial  lobe  very  small,  and  composed  of  four  obscurely  defined 
segments;  lateral  lobes  each  with  three  segments. 

"  Length  of  largest  known  specimen,  6  mm. ;  length  of  cephalic  shield, 
3.5  mm. ;  breadth  of  do.,  7  mm. ;  length  of  thorax,  1.25  mm. ;  breadth  of 
do.,  4.5  mm.;  length  of  pygidium,  75  mm.;  breadth  of  do.,  4  mm." — 
Ulrich,  1878. 

This  interesting  species  is  distinguished  from  all  American  and  Euro- 
pean species  of  the  genus  in  the  straightness  or  slight  concavity  of  the 
posterior  edge  of  the  cephalon,  and  in  the  relative  flatness  of  the  border. 
The  thorax  also  is  shorter  and  the  neck  spine  longer.  In  young  specimens 
such  as  the  original  type,  these  peculiarities  are  especially  marked.  In 
old  examples  the  posterior  edge  of  the  cephalon  turns  somewhat  pos- 
teriorly at  the  ends,  but  it  is  still  much  less  curved  than  in  all  other  species. 

Occurrence. — MARTINSBUEG  SHALE  (Eden  division).  Jordans  Knob, 
one  and  one-half  miles  northeast  of  Fort  Loudon,  Cowans  Gap,  five  miles 
northeast  of  McConnellsburg,  and  Tuscarora  Mountain,  two  and  one-half 
miles  southeast  of  McConnellsburg,  Pennsylvania.  Eden  shale  at  Cov- 
ington,  Kentucky. 

Collection. — TJ.  S.  National  Museum. 

CRYPTOLITHUS  EECURVUS  Ulrich  n.  sp. 
Plate  LVI,  Figs.  14-17 

Description. — This  new  species  has  been  discriminated  by  E.  0.  Ulrich, 
who  has  had  the  opportunity  of  studying  a  large  number  of  foreign  and 
American  specimens  of  this  genus.  Cryptolithus  recurvus  differs  from 


MARYLAND  GEOLOGICAL  SURVEY  335 

the  Trenton  form  usually  identified  as  Cryptolithus  tesselatus  Green  or 
Trinucleus  concentricus  Hall  by  the  great  width  and  decided  posterior 
recurvance  of  the  border  and  by  its  steeper  slope,  the  cephalon  as  a  whole 
being  therefore  more  convex.  C.  concentricus  resembles  it  in  the  last 
respect,  but  its  border  is  of  less  width  and  has  fewer  rows  of  pits.  Among 
the  differences  distinguishing  the  species  from  all  the  American  species 
of  the  genus  is  the  finely  punctate  and  not  reticulate  marking  of  the 
glabella  and  lateral  lobes. 

The  type  specimens  figured  were  collected  in  the  Eden  shale  at  Coving- 
ton,  Kentucky,  and  in  the  uppermost  Trenton  limestone  at  the  same  place. 

Occurrence. — MARTINSBURG  SHALE  (Eden  division).  Jordans  Knob, 
one  and  one-half  miles  northeast  of  Fort  Loudon,  Pennsylvania. 

Collection. — U.  S.  National  Museum. 

CRYPTOLITHUS  TESSELATUS  Green 

Plate  LI,  Figs.  19,  20 ;  Plate  LIT,  Fig.  17 

Cryptolithus  tesselatus  Green,  1832,  Monograph.  Trilobites  North  America, 

p.  73,  cast  38,  pi.  i,  fig.  4. 
Trinucleus  concentricus  Hall,  1847,  Pal.  New  York,  vol.  i,  p.  249,  pi.  Ixv, 

figs.  4a,  c. 
Trinucleus  concentricus  Weller,  1903,  Geol.  Surv.  New  Jersey,  Pal.,  vol.  iii, 

p.  192,  pi.  xiv,  figs.  3,  4. 

Description. — "  Head  semi-circular  or  subcrescent-form  in  outline,  the 
genal  angles  either  destitute  of  spines  or  produced  into  long,  slender, 
straight  spines.  Glabella  smooth,  very  prominent,  ovoid  in  outline,  the 
widest  portion  being  in  front,  with  a  short,  blunt  spine  posteriorly ;  cheeks 
smooth,  prominent,  but  depressed  considerably  below  the  glabella,  from 
which  they  are  separated  by  a  well-defined  dorsal  furrow;  eyes  wanting. 
The  entire  anterior  and  lateral  margins  of  the  head  are  surrounded  by  a 
broad,  somewhat  flattened  or  concave  border,  which  is  marked  in  front 
by  from  three  to  five  concentric  rows  of  deep,  rounded  pits ;  one  or  two 
additional  rows  are  introduced  on  the  sides,  and  toward  the  genal  angles 
the  pits  often  become  irregularly  scattered.  Length,  10  mm.;  width, 
15  mm. ;  convexity,  6  mm." — Weller,  1903. 
22 


336  SYSTEMATIC  PALEONTOLOGY 

Several  distinct  species  are  doubtless  included  in  the  many  descriptions 
that  have  been  published  under  the  name  of  Cryptolithus  tesselatus  and 
more  particularly  Trinucleus  concentricus.  The  specimens  from  the  base 
of  the  Martinsburg  shale,  however,  are  undoubtedly  the  same  specifically 
as  the  Trenton  forms  upon  which  Green  and  Hall  based  their  figures  and 
descriptions.  The  New  Jersey  Trenton  specimens  described  as  above 
by  Weller  likewise  belong  to  the  same  species. 

This  species  is  generally  quoted  as  ranging  from  the  base  of  the 
Trenton  to  the  middle  part  of  the  Maysville  group,  but  the  species  when 
restricted  will  probably  be  found  to  be  limited  to  the  Trenton  rocks.  In 
Pennsylvania  and  southward  it  occurs  in  the  Sinuites  zone  of  the  Trenton 
at  the  base  of  the  Martinsburg  shale. 

Occurrence. — MARTINSBURG  SHALE  (Sinuites  and  Corynoides  beds). 
Williamsport,  Maryland,  and  Chambersburg,  Pennsylvania. 

Collections. — Maryland  Geological  Survey,  U.  S.  National  Museum. 

Family  RAPHIOPHORIDAE 

Genus  AMPYX  Dalman 

AMPYX  (LoNCHODOMAs)  NORMALIS  (Billings) 
Plate  XLV,  Figs.  13,  14 

Ampyx  normalis  Billings,  1865,  Pal.  Foss.,  vol.  i,  Geol.  Surv.  Canada,  p.  295, 

text  fig.  286. 
Ampyx   (Lonchodomas)   normalis  Grabau  and  Shimer,  1910,  N.  A.  Index 

Fossils,  vol.  ii,  p.  259. 

Description. — "  Head,  without  the  movable  cheek,  triangular,  the  width 
about  one-third  greater  than  the  length;  fixed  cheeks,  gently  convex, 
smooth;  neck  segment  consisting  of  a  flat  plate,  inclining  backwards. 
The  glabella  elongate-ovate,  greatest  width  about  the  mid-length,  one- 
fourth  narrower  at  the  neck  segment,  the  apex  extending  a  little  over  the 
front  margin  of  the  head;  the  rostrum,  apparently,  when  perfect,  equal 
to  the  whole  length  of  the  head,  not  round  but  fluted ;  two  or  three  ovate 
or  nearly  circular  scars,  one  each  side  of  the  glabella  in  the  posterior  half. 

"  Pygidium  triangular,  width  twice  the  length,  the  two  posterior  sides 


MARYLAND  GEOLOGICAL  SURVEY  337 

gently  convex,  and  the  margin  abruptly  bent  down  or  bevelled  nearly 
vertically,  the  upper  edge  of  the  bevel  angular  and  with  indications  of  a 
slightly  elevated  linear  rim;  axis  very  depressed  convex  or  nearly  flat, 
its  width  at  the  anterior  margin  about  one-fourth  of  the  whole  width, 
extending  the  whole  length  or  nearly  so,  crossed  by  obscure  undulating 
furrows.  Side  lobes  gently  convex. 

u  Length  of  the  head  without  the  rostrum,  5  or  6  lines ;  length  of  the 
pygidium  about  4  lines." — Billings,  1865. 

Fragmentary  specimens  of  an  Ampyx  from  the  Echinospherites  bed  of 
Maryland  and  Pennsylvania  agree  so  closely  with  Billings'  figures  and 
description  that  they  are  believed  to  represent  the  same  species  in  spite 
of  the  differences  in  horizons. 

Occurrence. — CHAMBERSBURG  LIMESTONE  (Echinospherites  bed). 
Southern  Pennsylvania  and  at  Pinesburg  Station,  Maryland. 

Collection. — U.  S.  National  Museum. 

AMPYX  (LoNCHODOMAs)  HALLI  Billings 
Plate  XXXIX,  Figs.  9-11 

Ampyx  halli  Billings,  1862,  Kept.  Econ.  Geol.  Vermont,  p.  231,  text  fig.  365. 
Ampyx  halli  Billings,  1865,  Pal.  Foss.,  vol.  i,  Geol.  Surv.  Canada,  p.  24,  text 

figs.  25a-c. 
Lonchodomas  halli  Raymond,   1905,  Ann.  Carnegie  Mus.,  vol.   iii,  No.  2, 

p.  332,  pi.  x,  figs.  3-7. 

Description. — "  Cephalon. — Cranidium  triangular,  the  greatest  width 
at  the  neck  segment.  The  glabella  extends  about  half  its  own  length 
beyond  the  anterior  angles  of  the  fixed  cheeks,  and  is  then  prolonged  into 
ci  long,  fluted  spine,  which  curves  gently  upward.  This  spine  is  pris- 
matic, with  a  deep  furrow  on  each  of  its  four  sides.  The  furrow  on  the 
upper  side  extends  back  to  about  the  region  of  the  fixed  cheeks.  Glabella 
widest  at  the  anterior  angles  of  the  fixed  cheeks,  and  contracting  pos- 
teriorly, so  that  it  forms  about  one-fifth  of  the  whole  width  at  the  neck 
segment.  On  the  cast  there  are  two  small  nodes  on  each  side  of  the 
glabella  near  its  posterior  end,  one  pair  a  little  in  front  of  the  other.  A 
distinct  carina  extends  along  the  top  of  the  glabella  to  the  posterior  end 
of  the  dorsal  furrow  on  the  rostrum. 


338  SYSTEMATIC  PALEONTOLOGY 

"  Thorax. — A  specimen  from  Valcour  Island  retains  the  last  two  seg- 
ments of  the  thorax.  They  are  narrow,  extend  horizontally,  and  on  the 
pleura  are  deeply  grooved.  The  fourth  segment  is  5  mm.  wide,  .3  mm. 
long  and  the  axis  is  1.6  mm.  wide.  The  pygidium  of  the  same  specimen 
is  1.25  mm.  long,  4.3  mm.  Avide,  and  the  axis  is  1.3  mm.  wide  at  the 
anterior  end. 

"Pygidium. — The  pygidium  is  about  three  times  as  wide  as  long, 
usually  regularly  rounded  posteriorly,  sometimes  somewhat  triangular. 
Axis  wide,  prominent,  extending  to  the  posterior  end  of  the  pygidium. 
The  exfoliated  axis  shows  seven  to  ten  pairs  of  nodes  very  similar  to  those 
noticed  by  Euedemann  on  specimens  of  Loncliodomas  hastatus,  from 
Rysedorph  Hill.  The  pleura  show  three  or  four  pairs  of  rather  indistinct 
ribs.  The  margin  is  abruptly  deflected  all  around." — Eaymond,  1905. 

This  little  trilobite  is  one  of  the  common  fossils  of  the  Middle  Chazyan 
(Crown  Point)  limestone  of  the  Lake  Champlain  area,  the  types  coming 
from  Highgate  Springs,  Vermont. 

Occurrence. — STONES  RIVER  LIMESTONE  (Middle  division).  Penn- 
sylvania and  Maryland.  The  old  quarry  at  Chambersburg,  Pennsylvania, 
has  afforded  a  number  of  cephala  with  the  long  spines  preserved. 

Collections. — Maryland  Geological  Survey,  U.  S.  National  Museum. 

Order  OPISTHOPARIA 

Family  CORYNEXOCHIDAE  Angelin 

Genus   DOLIGHOMETOPUS  Angelin 

DOLICHOMETOPUS  Sp. 

Plate  XXVI,  Figs.  1-9 

Description. — More  or  less  distorted  cranida  and  pygidia  of  a  probable 
new  species  of  this  genus  of  trilobites  occurs  in  the  basal  part  of  the 
Elbrook  limestone.  Although  the  studies  of  this  and  allied  species  have 
not  progressed  far  enough  to  warrant  description,  illustrations  are  intro- 
duced on  pi.  XXVI  to  show  the  varying  aspect  of  such  fossils  under 
pressure. 


339 

Occurrence. — ELBROOK  LIMESTONE.    Small  quarry  on  the  eastern  out- 
skirts of  Waynesboro,  Pennsylvania. 
Collection. — U.  S.  National  Museum. 

Family  MESONACIDAE 

Genus  OLENELLUS  Hall 

OLENELLUS  THOMPSON!  (Hall) 

Plate  XXIV 

Olenus  thompsoni  Hall,  1859,  12th  Ann.  Kept.  New  York  State  Cab.  Nat. 

Hist.,  p.  59,  fig.  1,  p.  60. 
Olenellus  thompsoni  Walcott,  1886,  U.  S.  Geol.  Surv.  Bull.,  No.  30,  p.  167, 

pi.  xvii,  figs.  2,  4,  9;  pi.  xxii,  fig.  1;  pi.  xxiii,  fig.  1. 
Olenellus   thompsoni  Walcott,   1890,   10th   Ann.   Kept.   U.    S.   Geol.   Surv., 

pi.  Ixxxii,  figs.  1,  la;  pi.  Ixxxiii,  figs.  1,  la. 
Olenellus  thompsoni  Walcott,  1910,  Smithsonian  Misc.  Coll.,  No.  53,  p.  336, 

pi.  xxxiv,  fig.  9;  pi.  xxxv,  figs.  1-7. 

Description. — "  General  form  ovate,  the  length  and  breadth  being 
nearly  as  six  to  five.  Head  broad  lunate,  with  the  postero-lateral  angles 
much  extended ;  the  width  from  the  center  to  the  outer  margin  of  the  eye 
almost  equal  to  the  width  of  the  cheek.  Eyes  (which  are  much  crushed 
in  the  specimen)  elongate  semi-oval,  equal  in  length  to  the  space  between 
the  anterior  angles  and  the  frontal  margin;  glabella  distinctly  lobed, 
narrower  in  front. 

"  Thorax  with  the  lateral  lobes  about  once  and  a  half  as  wide  as  the 
middle  lobe,  consisting  of  14  articulations,  the  third  one  of  which  is  much 
longer  than  the  others,  and  curving  downwards  with  an  extension  reach- 
ing as  far  as  the  line  of  articulation  of  the  seventh  rib.  The  posterior 
articulations  are  bent  abruptly  backwards,  so  that  the  free  extremities  are 
parallel  with  the  axis.  Pygidium  small,  pointed,  without  visible  rings 
and  having  a  narrow  ridge  running  down  the  center." — Hall,  1859. 

Occurrence. — ANTIETAM  SANDSTONE  and  TOMSTOWN  LIMESTONE. 
Near  Smiths  burg,  and  at  Eakles  Mills  in  Washington  County,  Maryland. 
The  type  fossil  of  the  Lower  Cambrian  in  the  eastern  United  States  and 
Canada. 

Collections. — Maryland  Geological  Survey,  U.  S.  National  Museum. 


340  S  YSTEMATIC    PALEONTOLOGY 

Family  SOLENOPLEURIDAE 

Genus  HYSTRICURUS  Raymond 

HYSTEICUEUS  CONICUS  (Billings) 

Plate  XXXIII,  Figs.  10-12 

Bathyurus  conicus  Billings,  1859,  Canadian  Nat.  and  Geol.,  vol.  iv,  p.  266, 

text  fig.  12d. 
Bathyurus  conicus  Whitfield,  1889,  Bull.  Amer.  Mus.  Nat.  Hist.,  vol.  ii,  p.  61, 

pi.  xiii,  figs.  15-21. 
Hystricurus  conicus  Raymond,  1913,  Bull.  Victoria  Memorial  Mus.,  1,  p.  60, 

pi.  vii,  fig.  9. 

Description. — Glabella  conical,  rounded  at  the  anterior  and  almost 
straight  across  the  occipital  border ;  no  trace  of  glabellar  furrows ;  surface 
marked  by  larger  pustules,  slightly  more  than  their  own  diameter  apart. 

Pygidium  semicircular  with  the  anterior  margin  not  as  sharply  curved 
as  the  posterior,  which  is  bordered  by  a  narrow,  flattened  rim.  Surface 
strongly  trilobate,  with  the  axial  lobe  extending  to  the  posterior  margin 
where  it  is  obtusely  pointed.  Axial  lobe  marked  by  five  transverse,  short, 
sharply  elevated  rings,  each  of  which  is  marked  by  a  central  spine-like 
tubercle,  and  one  or  two  lateral  nodes.  Lateral  lobes  with  four  rings 
having  two  to  four  nodes  on  each. 

The  Maryland  specimens  referred  to  this  species  consist  of  pygidia 
having  the  same  general  outline  and  the  sharply  elevated  rings  orna- 
mented with  prominent  nodes.  The  species  has  hitherto  been  found  in 
the  Beekmantown  limestone  of  Canada,  Vermont  and  New  York. 

Occurrence. — BEEKMANTOWN  LIMESTONE  (Cryptozoon  steeli  zone). 
Vicinity  of  Williamsport  and  Hagerstown,  Maryland. 

Collection. — TJ.  S.  National  Museum. 

Family  BATHYURIDAE  Walcott 

Genus  GONIURUS  Raymond 

GONIURUS  CAUDATUS  (Billings) 

Plate  XXXVI,  Fig.  14 

Bathyurus  caudatus  Billings,  1865,  Pal.  Foss.,  vol.  i,  Geol.  Surv.  Canada, 

p.  261,  fig.  245. 
Goniurus  caudatus  Raymond,  1913,  Bull.  Victoria  Memorial  Mus.,  vol.   i, 

p.  66. 


341 

Description. — Pygidium  quite  convex,  with  a  strong  triangular  spine 
behind.  Axis  conical ;  occupying  less  than  one-third  of  the  width,  strongly 
convex  and  clearly  outlined  by  the  dorsal  furrow;  apex  of  axis  rounded 
and  with  four  or  five  rings.  Side  lobes,  with  four  or  five  broad  and  short 
ribs,  which  extend  about  half  way  to  the  margin.  A  smooth,  slightly  con- 
vex border  all  around  extends  backward,  and  forms  the  terminal  spine. 

The  well-marked  triangular  terminal  spine  of  this  species  causes  its 
identification  to  be  extremely  easy.  So  far  only  the  pygidium  of  the 
species  has  been  discovered. 

Occurrence. — BEEKMANTOWN  LIMESTONE  (Ceratopea  zone).  Vicinity 
of  Halfway,  Maryland.  The  types  are  from  the  Canadian  rocks  of  New- 
foundland. 

Collection. — U.  S.  National  Museum. 

Family  OLENIDAE 

Genus  TRIARTHRUS  Green 

TRIAETHEUS  FISCHEEI  Billings 

Plate  LI,  Fig.  16 

Triarthrus  fischeri  Billings,  1865,  Pal.  Foss.,  vol.  i,  Geol.   Surv.  Canada, 
p.  291,  text  fig.  280. 

Description. — A  small  cephalon  of  Triarthrus  found  in  the  Sinuites 
bed  at  Chambersburg,  Pennsylvania,  is  so  similar  to  Billings'  illustration 
of  T.  fischcri  copied  on  pi.  LI  that  it  is  believed  to  represent  the  same 
species  in  spite  of  the  supposed  difference  in  their  geological  horizons. 
It  is  possible  that  the  strata  in  which  the  type  of  T.  fischeri  occurred  are 
younger  than  now  believed,  and  again  it  would  not  be  surprising  if  this 
species,  like  many  others,  is  repeated  at  several  horizons  in  the  geologic 
column. 

Triarthrus  fischeri  differs  conspicuously  from  T.  becki  in  the  absence  of 
tubercles  along  the  median  line  of  the  axis.  The  types  are  from  the 
Chazyan  of  Newfoundland. 

Occurrence. — MAETINSBURG  SHALE  (Sinuites  bed).  Chambersburg, 
Pennsylvania. 

Collection. — U.  S.  National  Museum. 


342  SYSTEMATIC  PALEONTOLOGY 

TKIAETHKUS  BECKI  Green 
Plate  LI,  Figs.  17,  18;  Plate  LII,  Figs.  18-20;  Plate  LVI,  Figs.  7-13 

Triarthrus  fcecfci  Green,  1832,  Monograph  Trilobites  North  America,  p.  87, 

cast  34,  pi.  i,  fig.  6. 
Calymene  becki  Hall,  1847,  Pal.  New  York,  vol.  i,  pp.  237,  250,  pi.  Ixvi, 

figs.  2a-k. 

Description. — "  General  form  an  elongated  ellipse,  with  the  posterior 
extremity  narrower,  and  the  sides  often  straight ;  buckler  broadly  semioval, 
the  posterior  angles  rounded ;  glabella  of  equal  width  from  base  to  front, 
rounded  before,  deeply  trilobate  on  each  side,  with  a  prominent  thoracic 
ring  at  the  base;  frontal  lobe  narrowed  longitudinally;  thorax  with  13 
segments,  those  of  the  central  lobe  with  a  short  spine  or  tubercle  upon  .the 
back,  those  of  the  lateral  lobes  deeply  grooved  along  the  center;  caudal 
shield  with  six  or  seven  segments  in  the  middle  lobe,  and  five  in  the  lateral 
lobes;  posterior  extremity  obtuse." — Hall,  1847. 

Specimens  of  Triarthrus  occur  at  several  horizons  in  the  Martinsburg 
shale  of  Maryland,  and  although  their  preservation  is  not  always  good,  all 
seem  to  have  the  tubercle  on  the  center  of  each  axial  segment,  character- 
istic of  the  well-known  and  widely  distributed  T.  becJci  Green. 

Occurrence. — MARTINSBUEG  SHALE.  Chambersburg,  Pennsylvania 
(Sinuites  bed).  Williamsport,  Maryland  (Corynoides  bed).  Fort 
Loudon,  Pennsylvania,  and  Eickard  Mountain,  Maryland  (Eden 
division). 

Collections. — Maryland  Geological  Survey,  II.  S.  National  Museum. 

Family  ASAPHIDAE 

Genus  ISOTELUS   DeKay 

ISOTELUS  STEGOPS  Green 

Plate  LVI,  Figs.  3,  4 

Isotelus  stegops  Green,  1832,   Monograph   Trilobites  North  Amer.,   p.   71, 
cast  26,  27. 

Description. — The  species  of  Isotelus  occurring  in  the  Eden  shale  of  the 
Ohio  Valley  hitherto  referred  to  Isotelus  gigas  DeKay  seems  to  represent 
a  distinct  species  for  which  the  name  Isotelus  stegops  Green  is  here 


MARYLAND  GEOLOGICAL  SURVEY  343 

adopted.  According  to  the  researches  of  E.  0.  Ulrich  as  yet  unpublished, 
Green's  casts  of  Isotelus  stegops,  the  originals  of  which  came  from  New- 
port, Kentucky,  show  no  good  differences  from  the  Eden  shale  species  of 
that  region. 

Compared  with  Isotelus  maximus  Locke,  which  7.  stegops  most  closely 
resembles,  the  Eden  form  has  the  eye  further  forward,  smaller  spines,  and 
the  flattened  border,  especially  of  the  pygidium,  less  distinct. 

Occurrence. — MARTINSBURG  SHALE  (Eden  division).  Jordans  Knob, 
one  and  one-half  miles  northeast  of  Fort  Loudon,  and  other  localities  in 
Pennsylvania. 

Collection. — U.  S.  National  Museum. 

ISOTELUS  MEGISTOS  Locke 

Plate  LVIII,  Figs.  10, 11 

Isotelus  megistos  Locke,  1842,  Amer.  Jour.  Scl.,  vol.  xlii,  p.  366,  pi.  iii,  fig.  9. 
Asaphus    (Isotelus)    megistos  Meek,  1873,  Geol.   Surv.  Ohio,  Pal.,  vol.  I, 
p.  159,  pi.  xiv,  fig.  13. 

Description. — Under  this  name  and  also  those  of  Isotelus  maximus 
Locke  and  7.  gigas  DeKay,  a  number  of  distinct  species  ranging  through 
the  Mohawkian  and  Cincinnatian  have  undoubtedly  been  confused,  with 
the  result  that  these  names  have  little  stratigraphic  significance.  The 
discrimination  of  these  species  has  been  undertaken  by  E.  0.  Ulrich, 
whose  work  upon  them  is  still  in  manuscript  form.  He  has  determined 
that  the  fragments  found  in  the  Fairview  deposits  of  Maryland  and 
Pennsylvania  are  identical  specifically  with  the  types  of  Locke's  Isotelus 
megistos  and  also  with  the  specimen  illustrated  later  by  Meek  as  Asaphus 
(Isotelus)  megistos. 

Formerly  the  separation  of  these  species  was  based  upon  the  presence 
or  absence  of  the  genal  spine,  but  it  is  now  known  that  each  species 
contains  spinuous  and  aspinous  forms,  the  difference  between  the  two 
being  presumably  that  of  sex.  The  aspinous  ( ?  female)  forms  of  these 
several  species  are  quite  difficult  to  distinguish  from  each  other,  but  the 
spinous  examples  show  good  characters  of  differentiation.  Thus,  in  the 
case  of  7.  maximus  and  7.  megistos,  long  considered  synonymous,  the  free 


344  SYSTEMATIC  PALEONTOLOGY 

cheeks  of  each  are  different.  In  7.  megistos  the  base  of  the  spine  is  much 
wider  and  it  tapers  much  more  rapidly.  The  hypostoma  furnishes  further 
differences,  for  in  7.  megistos  it  shows  coarser  venations,  the  inner  edges 
of  the  limb  are  straighter,  and  the  whole  hypostoma  is  relatively  longer. 

Occurrence. — MARTINSBURG  SHALE  (Fairview  division,  Orthorhyn- 
chula  bed).  Pennsylvania  to  Tennessee. 

Collection. — TJ.  S.  National  Museum. 

ISOTELUS  GIGAS  DeKay 

Plate  XLVIII,  Figs.  23-25 

Isotelus  gigas  DeKay,  1824,  Annals  Lyceum  Nat.  Hist.  New  York,  vol.  i, 

p.  176,  pi.  xii,  fig.  1. 

Isotelus  gigas  Hall,  1847,  Pal.  New  York,  vol.  i,  p.  231,  pi.  Ix-lxiii. 
Isotelus  gigas  Weller,  1903,  Pal.  New  Jersey,  vol.  iii,  p.  192,  pi.  xiv,  figs.  6,  7. 
Isotelus  gigas  Raymond,  1914,  Bull.  Mus.  Comp.  Zool.,  vol.  Iviii,  p.  248,  pi.  i, 

figs.  1,  2,  pi.  ii,  figs.  2-5;  pi.  iii,  fig.  3. 

Description. — "  Outline  of  an  entire  individual  subelliptical,  with  the 
anterior  and  posterior  extremities  somewhat  pointed;  the  trilobation 
nearly  obsolete.  Head  subtriangular  to  semi-elliptical  in  outline,  convex, 
slightly  flattened  in  front;  the  anterior  margin  rather  sharply  rounded; 
facial  sutures  meeting  at  an  angle,  at  or  just  behind  the  frontal  margin, 
from  this  point  they  describe  a  broad,  subarcuate  curve,  and  after  passing 
around  the  eyes,  they  curve  outward  and  then  downward,  intersecting 
the  posterior  margin  at  some  distance  outside  of  the  eyes;  glabella 
obscurely  denned  and  more  obscurely  lobed;  occipital  furrow  and  seg- 
ment obsolete:  free  cheeks  marked  by  an  intramarginal  furrow,  above 
which  their  general  surface  is  elevated  into  a  more  or  less  conspicuous 
node,  crowned  by  the  eye.  Thorax  with  a  broad  axial  lobe,  occupying 
more  than  one-third  the  width,  consisting  of  eight  segments.  Pygidium 
subtriangular  in  outline  of  nearly  the  same  size  and  shape  as  the  head, 
its  lobation  very  obscure,  especially  in  the  larger  individuals,  the  dorsal 
furrows  being  hardly  distinguishable ;  axis  much  narrower  at  its  anterior 
extremity  than  the  axis  of  the  thorax,  tapering  rapidly  to  the  obtusely 
rounded  posterior  extremity,  which  lies  at  about  one-fourth  the  length  of 


MARYLAND  GEOLOGICAL  SURVEY  345 

the  pygidium  from  the  posterior  margin;  plurae  convex,  smooth  in  the 
larger  individuals,  but  in  younger  ones  marked  by  about  ten  obscure 
segments,  which  also  continue  across  the  axis;  the  entire  margin  of  the 
pygidium,  except  where  it  joins  the  thorax,  bordered  by  a  rather  broad, 
slightly  depressed,  marginal  border;  the  anterior,  lateral  angles  bent 
abruptly  downward." — Weller,  1903. 

This  frequently  quoted  trilobite  has  been  often  described  and  illustrated 
with  the  result  that  several  species  have  undoubtedly  been  confused  under 
the  name.  The  specimens  from  the  Cumberland  Valley  are  fragmentary, 
although  they  agree  so  far  as  they  go  with  the  above  description.  The 
complete  examples  figured  are  from  the  type  area  of  the  species  in  New 
York. 

Occurrence. — CHAMBERSBURG  LIMESTONE  (Christiania  bed).  Penn- 
sylvania, Maryland,  and  Virginia. 

Collections. — Maryland  Geological  Survey,  U.  S.  National  Museum. 

.       ISOTELUS  Sp. 

Plate  XXXVII,  Fig.  9 

Description. — A  single  imperfect  free  cheek  of  Isolelus  has  been  found 
in  the  Frederick  limestone  and  is  figured  in  the  present  report.  It  is  of 
little  value  in  determining  the  age  of  this  limestone,  as  species  of  this 
general  type  have  a  long  geologic  range. 

Occurrence. — FREDERICK  LIMESTONE.  Just  east  of  Frederick,  Mary- 
land. 

Collection. — U.  S.  National  Museum. 

Genus  ASAPHELLUS  Callaway 

ASAPHELLUS  GYRACANTHUS  Eaymond 

Plate  XXXII,  Figs.  8-10 

Asaphus  canalis?  Cleland,  1900   (not  Conrad),  Bull.  Amer.  Pal.,  vol.  ill, 

p.  128,  pi.  xvi,  figs.  7,  8. 

Isotelus  canalis  Weller,  1902,  Pal.  New  Jersey,  vol.  iii,  p.  132,  pi.  v,  figs.  5,  6. 
Asaphellus  gyracantJius  Raymond,  1910,  Ann.  Carnegie  Mus.,  vol.  vii,  No.  1. 

p.  39,  pi.  xiv,  figs.  5-7. 


346  SYSTEMATIC  PALEONTOLOGY 

Description. — Entire  cephalon  unknown.  Free  cheek  broad,  flat,  tri- 
angular in  outline,  bearing  a  long  spine  at  the  genal  angle.  Glabella  flat 
with  a  narrow  depressed  border  in  front  and  scarcely  any  traces  of  dorsal 
furrows.  Eyes  prominent  with  their  longest  diameter  5  mm.  and  between 
them  a  minute  pustule.  The  pygidium  is  uniformly  convex  with  a 
narrow,  depressed  border,  and  is  semicircular  in  outline.  Its  axial  lobe  is 
narrow  and  improminent,  with  traces  of  three  or  four  rings  at  the  anterior 
end.  Size  of  the  pygidium  varies  from  10  mm.  in  width  and  7  mm.  in 
length  to  50  mm.  by  40  mm.  Hypostoma  quadrangular. 

This  species  much  resembles  Hemigyraspis  collieana  Kaymond  with 
fragments  of  which  it  is  associated  in  Maryland,  but  its  cephalon  is  longer 
and  narrower  and  the  axial  lobe  of  the  pygidium  not  so  prominent. 

Occurrence. — BEEKMANTOWN  LIMESTONE  (Stonehenge  member). 
Vicinity  of  Hagerstown,  Maryland.  Tribes  Hill  limestone  of  New  York 
and  upper  part  of  Kittatinny  limestone  of  New  Jersey. 

Collection. — U.  S.  National  Museum. 

Genus  HEMIGYRASPIS  Raymond 
HEMIGYRASPIS  COLLIEANA  Eaymond 

Plate  XXXII,  Figs.  11-15 

Asaphus  marginalis  Collie  (not  Hall),  1903,  Bull.  Geol.  Soc.  Amer.,  vol.  xiv, 

p.  413. 
Hemigyraspis  collieana  Raymond,  1910,  Ann.  Carnegie  Mus.,  vol.  vii,  p.  41, 

pi.  xiv,  figs.  9-13. 

Description. — "  Cephalon  short  and  wide,  glabella  smooth,  not  out- 
lined, no  glabellar  furrows.  Neck-furrow  shallow,  hardly  visible.  Eyes 
nearly  halfway  to  the  front  of  the  cephalon,  large,  very  far  apart.  Between 
the  eyes  is  a  small  median  tubercle.  Free  cheeks  short,  wide,  with  long 
narrow  spines  at  the  genal  angles.  The  anterior  limb  of  the  facial  suture 
meets  the  frontal  margin  in  front  of  the  eye.  There  is  a  narrow  depressed 
border  on  the  front  of  the  cranidium. 

"Axial  lobe  of  thorax  one-third  the  total  width;  pleura  grooved. 
Pygidium  short,  wide,  semicircular  in  outline.  Axial  lobe  narrow,  rather 
prominent,  showing  traces  of  two  or  three  rings.  Pleural  lobes  convex, 


MARYLAND  GEOLOGICAL  SURVEY  347 

without  traces  of  ribs.  Border  narrow,  concave;  doublure  narrow,  con- 
vex. Hypostoma  quadrangular,  widest  in  front,  central  portion  convex, 
with  a  furrow  and  narrow  border  around  the  sides  and  posterior  end. 
Surface  of  all  parts,  including  the  hypostoma,  covered  with  imbricating 
striae. 

"One  pygidium  is  9.5  mm.  long  and  18  mm.  wide;  a  larger  one  is 
14  mm.  long  and  28  mm.  wide." — Eaymond,  1910. 

As  noted  by  Raymond  this  species  much  resembles  Asaphus  gyracanthus, 
but  its  cephalon  is  shorter  and  wider,  the  eyes  are  farther  apart  and  the 
axial  lobe  of  the  pygidium  is  much  more  prominent. 

Occurrence. — BEEKMANTOWN  LIMESTONE  (Stonehenge  member). 
Hagerstown,  Maryland  and  Bellefonte,  Pennsylvania. 

Collection. — U.  S.  National  Museum. 

Genus  SYMPHYSURUS  Goldfuss 

SYMPHYSURUS  CONVEXUS  (Cleland) 

Plate  XXXII,  Figs.  16-18 

Asaphus  convexus  ?  Cleland,  1900,  Bull.  Amer.  Pal.,  vol.  iii,  p.  128   (256), 

pi.  xvi,  fig.  4. 

Bathyurus  sp.  Cleland,  1900,  Idem.,  pi.  xvi,  fig.  9. 
Illaenurus  columbiana  Weller,  1903,  Pal.  New  Jersey,  vol.  iii,  p.  133,  pi.  v, 

figs.  1-4. 

Bathyurus  f  levis  Cleland,  1903,  Bull.  Amer.  Pal.,  vol.  iv,  p.  36,  pi.  ii,  figs.  1,  2. 
Symphysurus  convexus  Raymond,  1910,  Ann.  Carnegie  Mus.,  vol.  vii,  No.  1, 

p.  42,  pi.  xiv,  figs.  14-16. 

Description-. — Entire  cephalon  unknown ;  glabella  oblong,  convex,  with 
the  eyes  located  halfway  between  the  front  and  back.  A  small  median 
tubercle  present,  below  the  eyes.  Thorax  unknown,  but  its  axial  lobe  is 
probably  narrow.  Pygidium  semicircular  with  a  distinct  axial  lobe. 
Several  indistinct  annulations  are  present. 

The  types  of  both  this  species  and  its  synonym  Bathyurus  ?  levis 
Cleland  were  obtained  in  the  Tribes  Hill  limestone  at  Fort  Hunter,  New 
York.  The  species  was  identified  by  Weller  in  the  Canadian  portion  of 
the  Kittatinny  limestone  at  Columbia,  New  Jersey,  and  under  the  belief 
that  the  species  belonged  to  Illaenurus,  the  new  name  Illaenurus  colum- 
biana  was  proposed,  the  name  Illaenurus  convexus  being  preoccupied. 


348  SYSTEMATIC  PALEONTOLOGY 

Occurrence. — BEEKMANTOWN     LIMESTONE     (Stonehenge     member). 
Hagerstown  and  Funkstown,  Maryland. 
Collection.— 1J.  S.  National  Museum. 

Genus  ONCHOMETOPUS  Schmidt 
ONCHOMETOPUS  SIMPLEX  Eaymond  and  Narraway 

Plate  XLVII,  Fig.  18 

Onchometopus  simplex  Raymond  and  Narraway,  1910,  Ann.  Carnegie  Mus., 
vol.  vii,  p.  51,  pi.  xvi,  figs.  6-8. 

Description. — "  Cranidium  moderately  convex,  slightly  incurved  at  the 
front.  Glabella  flat,  obscurely  defined,  expanding  in  front  of  the  eyes 
and  extending  to  the  anterior  margin;  glabellar  furrows  absent,  dorsal 
furrows  present  back  of  the  eyes,  very  shallow.  Neck-furrow  absent. 
Eyes  of  medium  size,  situated  a  trifle  more  than  their  own  length  in  front 
of  the  posterior  margin.  Behind  the  eyes  there  is  a  small  median  tubercle 
on  the  glabella.  Free  cheeks  rounded  at  the  genal  angles. 

"  Thorax  of  eight  flat  segments.  Axial  lobe  a  little  more  than  one-third 
the  total  width.  Pleura  with  shallow  grooves. 

"  Pygidium  rounded  in  outline,  three-fifths  as  long  as  wide.  Axial 
lobe  obscurely  defined,  the  posterior  end  usually  a  little  more  prominent 
than  the  other  portions.  There  are  no  annulations.  The  surface  is  uni- 
formly convex,  without  concave  border. 

"  This  species  is  similar  to  Onchometopus  obtusus  (Hall)  of  the  Chazy, 
but  the  shell  lacks  the  very  coarse  punctae  of  that  form,  and  there  are 
fewer  traces  of  glabellar  furrows.  It  differs  from  Onchometopus  susae 
(Whitfield)  in  having  a  longer  pygidium  with  a  narrower  and  more 
distinct  axial  lobe/ 

"  Onchometopus  may  be  readily  distinguished  from  Isotelus  by  the 
presence  of  a  median  tubercle  on  the  glabella,  the  absence  of  a  concave 
border  on  both  cephalon  and  pygidium,  and  by  the  somewhat  narrower 
axial  lobe  in  the  thorax." — Raymond  and  Narraway,  1910. 

The  interesting  Maryland  trilobite  referred  to  the  above  species  differs 
from  all  other  Chambersburg  forms  in  the  absence  of  the  concave  border 


MARYLAND  GEOLOGICAL  SURVEY  349 

on  both  the  cephalon  and  pygidium.  Although  imperfect  it  agrees  fairly 
well  in  outline  with  the  types  of  Onclwmetopus  simplex. 

Occurrence.— CHAMBERSBURG  LIMESTONE  (Nidulites  bed).  Wilson, 
Maryland.  Black  River  limestone  of  Minnesota  and  Pennsylvania. 

Collection. — II.  S.  National  Museum. 

Family  ILLAENIDAE 

Genus  ILLAENUS  Dalman 

ILLAENUS  AMERICANUS  Billings 

Plate  LI,  Figs.  26-29 

Illaenus  americanus  Billings,  1859,  Canadian  Nat.  Geol.,  vol.  iv,  p.  371. 
Illaenus  americanus  Billings,  1865,  Pal.  Fossils,  vol.  i,  Geol.  Surv.  Canada, 

p.  329,  figs.  316a-d,  318. 
Illaenus  americanus  Raymond  and  Narraway,  1908,  Ann.  Carnegie  Mus., 

vol.  iv,  Nos.  3,  4,  pi.  Ix,  figs.  1-3. 

Description. — "  Oblong,  distinctly  tri-lobed ;  length  two  or  three  inches ; 
width  from  three-fifths  to  five-sixths  the  length. 

"  Head  large,  strongly  convex,  its  height  usually  a  little  greater  than 
its  length  measured  on  a  straight  line,  sometimes  abruptly  bent  down  at 
less  than  half  the  length  from  behind,  often  uniformly  arched  from  the 
front  to  the  posterior  margin,  equal  to  about  one-fourth  of  a  sphere; 
length  from  front  to  posterior  margin  about  two-thirds  the  width  between 
the  cheek  angles  in  a  straight  line.  The  glabella  is  moderately  convex; 
the  dorsal  furrows  extend  from  one-fourth  to  a  little  more  than  one-third 
the  whole  length  of  the  head,  measured  on  the  curve,  and  have  an  obscure 
sigmoid  curve,  at  first  outwards  and  then  inwards,  their  anterior  ex- 
tremities usually  turning  a  little  outwards;  they  are  distant  from  each 
other  not  quite  one-half  the  whole  width  of  the  head.  The  eyes  are  of 
moderate  size,  about  two  lines  in  length,  about  half  their  length  from  the 
posterior  margin,  and  half  the  width  of  the  glabella  from  the  dorsal 
furrows.  The  cheek  angles  are  rounded,  and  the  posterior  margin  of  the 
head  makes  with  the  lateral  lower  margin,  as  seen  in  a  side  view  usually  a 
right  angle,  but  in  some  specimens  an  obtuse  angle  of  nearly  100°,  owing 
to  the  variable  extent  to  which  the  front  part  of  the  head  is  produced 


350  SYSTEMATIC  PALEONTOLOGY 

downwards.  In  some  the  portion  of  the  posterior  margin  outside  of  the 
eye  curves  forwards,  and  brings  the  cheek  angle  to  a  position  in  front 
of  the  eye.  In  others,  it  is  behind  the  eye.  The  space  between  the  eye 
and  the  dorsal  furrows  is  convex,  and  the  eye  itself  seems  to  be  rather 
strongly  protuberant  or  subconical.  The  movable  cheek  is  subtriangular, 
its  width  at  the  posterior  margin  about  one  and  a  half  the  distance  of  the 
eye  from  the  dorsal  furrow,  its  length  along  the  lower  margin  a  little 
greater  than  its  posterior  width.  The  anterior  margin  of  the  whole  head 
is  uniformly  rounded,  with  the  exception  of  a  slight  concave  curve  just 
outside  of  the  suture.  In  some  specimens  in  which  .the  front  part  of  the 
head  is  most  abruptly  bent  down  the  middle  portion  of  the  front  margin 
is  depressed  convex  or  nearly  straight. 

"  Thorax  with  ten  segments.  Axis  moderately  convex,  from  a  little 
more  than  one-third  to  nearly  one-half  the  width  of  the  whole  animal,  a 
little  wider  at  the  anterior  than  at  the  posterior  segment ;  the  sides  some- 
times straight,  and  sometimes  slightly  curved  outwards.  On  each  side 
of  the  axis  there  is  a  flat  space  between  the  side  of  the  axis  and  the  bend 
of  the  pleurae.  The  width  of  this  space  is  between  one-third  and  one-half 
the  width  of  the  axis.  The  pleurae  are  bent  at  the  fulcra  at  an  angle 
which  varies  in  different  individuals,  from  25°  to  45°,  and  at  nearly 
one-half  their  length  from  the  side  of  the  axis. 

"  Pygidium  usually  a  little  shorter  than  the  thorax ;  varying  from 
moderately  to  rather  strongly  convex;  the  posterior  margin  broadly  and 
uniformly  rounded;  the  anterior  angles  truncated  nearly  half  the  whole 
length  of  the  pygidium ;  the  straight  sides  formed  by  the  truncation  form- 
ing an  angle  of  from  40°  to  60°  with  the  longitudinal  axis  of  the  body. 
The  axis  of  the  pygidium  is  well  defined  at  the  anterior  margin  by  the 
dorsal  furrows,  which  die  out  at  about  one-third  or  one-half  the  length, 
converging  towards  each  other,  and  sometimes  obscurely  defining  the 
apex."— Billings,  1865. 

Occurrence. — MARTINSBURG  SHALE  (Sinuites  bed).  Chambersburg, 
Pennsylvania.  Trenton  limestone  of  Ottawa,  Canada,  and  many  other 
localities. 

Collection. — IT.  S.  National  Museum. 


MARYLAND  GEOLOGICAL  SURVEY  351 

Genus  BUMASTUS  Murchison 

BUMASTUS  TRENTONENSIS  Emmons 

Plate  LI,  Figs.  30-33 

Bumastus  trentonensis  Emmons,  1842,  Nat.  Hist.  New  York,  Geol.,  vol.  ii, 

p.  390,  fig.  1. 
Bumastus  trentonensis  (part)  Clarke,  1897,  Geol.  Minnesota,  vol.  iii,  pt.  2, 

p.  718. 
Bumastus   milleri   Raymond   and   Narraway,    1908,   Ann.    Carnegie   Mus., 

vol.  iv,  p.  249,  pi.  Ixi,  figs.  9,  10,  pi.  Ixii,  figs.  3-5. 

Description. — Emmons'  figure  of  his  type  specimen  of  Bumastus  tren- 
tonensis represents  an  example  with  eight  segments  to  the  thorax.  Before 
this  specimen  could  be  restudied  it  was  lost  and  the  validity  of  the  name 
has  been  questioned.  It  is  unnecessary  to  enter  into  a  history  of  the 
synonymy  of  this  species,  as  this  was  fully  discussed  in  1908  by  Raymond 
and  Narraway.  However,  a  species  of  Bumastus  with  eight  segments 
occurs  in  the  Trenton  limestone  of  New  York  which,  according  to  the 
present  arrangement  of  species  of  the  genus,  has  no  name.  This  species 
agrees  with  Emmons'  figure  fairly  well  and  it  seems  reasonable  to  retain 
his  name  of  Bumastus  trentonensis. 

Occurrence. — MARTINSBURG  SHALE  (Sinuites  bed).  Chambersburg, 
Pennsylvania.  Trenton  limestone  of  New  York. 

Collection. — U.  S.  National  Museum. 

Family  DIKELOCEPHALIDAE 

Genus  SAUKIA  Walcott 
SAUKIA  STOSEI  Walcott 
Plate  XXVII,  Figs.  6-8 

t  Saukia  stosei  Walcott,  1914,  Smithsonian  Misc.  Coll.,  vol.  Ivii,  No.  13,  p.  384, 
pi.  Ixix,  figs.  3-5;  pi.  Ixx,  figs.  12,  12a. 

Description. — "  This  species  belongs  to  the  8.  pepinensis  form  of 
•Saukia,  and  is  most  nearly  related  to  Saukia  fallax,  but  it  has  a  propor- 
tionately larger  palpebral  lobe.  The  associated  pygidium  differs  from  the 
pygidium  found  with  8.  fallax  in  Texas  in  having  a  longer  axial  lobe, 
and  the  surface  is  strongly  granulated  instead  of  being  smooth  as  in 
S.  fa  llax."— Walcott. 


352  SYSTEMATIC  PALEONTOLOGY 

Occurrence. — CONOCOCHEAGUE  LIMESTONE.    Near  Scotland,  Franklin 
County,  Pennsylvania.    Near  Funkstown,  Maryland. 

Collections. — Maryland  Geological  Survey,  U.  S.  National  Museum. 

Family  PROETIDAE 

Genus  PROETUS  Steininger 

PROETUS  LATIMAEGINATUS  Weller 

Plate  LI,  Figs.  21-25 

Proetus  latimarginatus  Weller,  1903,  Geol.  Surv.  New  Jersey,  Pal.,  vol.  iii, 
p.  195,  pi.  xiv,  figs.  17-24  (?25). 

Description. — "  Head  sublunate  in  outline,  the  genal  angles  produced 
into  long,  sharp  spines.  Glabella  elevated,  broadly  subconical,  rounded  in 
front;  lateral  furrows  nearly  obsolete  exteriorly,  but  sometimes  their 
position  is  indicated  by  dark  lines  on  the  surface,  which  seem  to  indicate 
an  internal  thickening  of  the  test;  the  two  anterior  pairs  are  short  and  lie 
in  front  of  the  eye-lobes ;  they  are  close  together,  and  are  directed  obliquely 
backward  from  the  margin  of  the  glabella;  the  posterior  pairs  are  more 
conspicuous  than  the  others,  and  are  sometimes  marked  by  slight  depres- 
sions ;  they  are  situated  a  little  in  front  of  the  middle  of  the  eye-lobes,  and 
are  directed  obliquely  backward  from  the  margin  of  the  glabella,  becoming 
more  curved  posteriorly,  joining  the  occipital  furrow  at  nearly  right 
angles.  The  dorsal  furrow  well  defined  throughout.  Occipital  furrow 
sharply  impressed,  deeper  than  the  dorsal  furrow.  Occipital  segment 
with  subparallel  margins,  scarcely  as  highly  elevated  as  the  glabella, 
marked  by  a  small,  rounded  tubercle  at  its  central  point.  Palpebral  lobes 
of  moderate  width,  sub-semicircular  in  outline,  depressed  below  the  level 
of  the  glabella.  Facial  sutures  curving  into  the  margin  of  the  glabella, 
both  in  front  and  behind  the  palpebral  lobes;  posteriorly  they  intersect 
the  margin  of  the  head  close  to  the  axial  lobe;  in  front  of  the  palpebral 
lobes  they  curve  outward  nearly  to  the  margin  of  the  head,  where  they 
make  a  rather  sharp  bend  and  recurve  inwardly,  intersecting  the  anterior 
margin  at  some  distance  from  its  median  point.  Anterior  limb  of  the 
cranidium  broad,  with  a  convex  marginal  border,  between  which  and  the 


MARYLAND  GEOLOGICAL  SURVEY  353 

glabella  there  is  a  rather  broad,  shallow,  concave  furrow.  Free  cheeks 
depressed-convex,  with  the  eyes  abruptly  elevated,  marked  by  a  rather 
broad  marginal  border  on  both  the  lateral  and  posterior  margins,  on  the 
inner  side  of  which  there  is  a  rather  sharply  impressed  furrow.  Pygidium 
small,  sub-semicircular  in  outline;  the  posterior  margin  regularly 
rounded ;  the  anterior  margin  straight  nearly  to  the  lateral  angles,  where 
it  is  curved  backward.  Axis  narrow,  not  reaching  to  the  posterior  margin, 
marked  by  six  or  seven  annulations.  Pleurae  convex,  much  depressed 
below  the  axis,  marked  by  five  or  six  grooved  segments,  only  the  anterior 
two  or  three  of  which  reach  the  margin  of  the  pygidium.  Thorax  UEH 
known.  The  entire  surface  of  well-preserved  specimens  is  finely  grami- 
lose."— Weller,  1903. 

The  specimens  from  the  basal  Martinsburg  shale  are  not  as  complete  as 
the  types  upon  which  the  above  description  was  based,  but  there  seems 
little  doubt  of  their  specific  identity. 

Occurrence. — MARTINSBURG  SHALE  (Sinuites  bed).  Chambersburg, 
Pennsylvania.  Trenton  limestone  of  New  Jersey. 

Collection. — U.  S.  National  Museum. 

Genus  CYPHASPIS  Burmeister        v ' 
CYPHASPIS  MATUTINA  Euedemann 

Plate  LI,  Figs.  12-14 

Cyphaspis  matutina  Ruedemann,  1901,  New  York  State  Mus.  Bull.,  No.  49, 
p.  62,  pi.  iv,  figs.  5-7. 

Description. — "  The  glabella  is  short,  roundish,  subquadrangulaf, 
moderately  and  uniformly  convex,  sloping  equally  to  all  sides ;  surrounded 
by  deep  dorsal  furrows  and  an  equally  deep  frontal  furrow.  Three  pair's 
of  glabellar  furrows  are  discernible,  the  first  two  faint,  short  and  oblique, 
the  third  semicircular,  extending  to  the  occipital  furrow,  and  separating 
a  pair  of  less  convex  lobes,  which  extend  a  little  beyond  the  lateral  margin 
of  the  first  and  second  lobes ;  the  broad  border  slopes  steeply  to  a  narrow 
rim,  somewhat  upturned  at  the  margin.  The  glabella  and  rim  are 
apparently  completely  smooth,  but  show  under  the  glass  fine  transverse 


354  SYSTEMATIC  PALEONTOLOGY 

striae.  Neck  ring  nearly  flat,  depressed,  with  a  central  tubercle ;  occipital 
furrow  distinct,  nearly  straight.  Sutures  begin  at  the  anterolateral  angles 
of  the  margin,  extend  in  the  direction  of  the  second  glabellar  lobe  to  near 
the  glabella,  and  then  curve  backward." — Euedemann,  1901. 

This  species  was  based  upon  two  small  cranidia,  both  of  which  are 
illustrated  in  the  present  report.  The  material  here  identified  with 
C.  matutina  consists  of  imperfect  cranidia  only,  so  that  nothing  further 
can  be  added  to  the  specific  description. 

Occurrence. — MAETINSBURG  SHALE  (Sinuites  bed).  Chambersburg, 
Pennsylvania.  Eysedorph  conglomerate  at  base  of  Trenton,  Kensselaer 
County,  New  York. 

Collection. — U.  S.  National  Museum. 

Family  LICHADIDAE 

Genus  AMPHILIGHAS  Raymond 

AMPHILICHAS  TRENTONENSIS  (Conrad) 

Plate  LI,  Figs.  8-10 

Asaphus  f  Trentonensis  Conrad,  1842,  Jour.  Acad.  Nat.  Sci.  Philadelphia, 

vol.  viii,  p.  277,  pi.  xvi,  fig.  16. 
Platynotus  trentonensis  Hall,  1847,  Pal.  New  York,  vol.  i,  p.  235,  pi.  Ixiv, 

figs.  la-d. 
Platymetopus   trentonensis   Weller,    1903,    Geol.    Surv.   New   Jersey,    Pal., 

vol.  iii,  p.  200,  pi.  xv,  figs.  17-19. 

Description. — "  Head  ventricose,  the  curve  along  the  median  line  from 
the  posterior  to  the  anterior  margins  being  very  nearly  a  semicircle, 
sub-semicircular  in  outline,  attaining  a  breadth  of  35  or  40  mm.  The 
glabella  very  large,  occupying  nearly  the  entire  breadth  of  the  cranidium, 
strongly  protuberant  in  front;  with  a  single  pair  of  glabellar  furrows, 
which  originate  at  the  anterior,  lateral  margins,  and,  after  curving 
inward,  then  backward  and  then  slightly  outward  again,  forming  some- 
thing more  than  a  semicircle,  they  join  the  occipital  furrow,  dividing  the 
glabella  into  three  lobes;  the  frontal  or  median  lobe  is  broad  in  front, 
becoming  narrower  posteriorly  to  a  point  back  of  the  middle  of  the  head, 


MARYLAND  GEOLOGICAL  SURVEY  355 

and  then  again  broadens  out,  becoming  nearly  as  wide  on  the  occipital 
furrow  as  it  was  on  the  anterior  margin;  the  two  lateral  lobes  about  as 
prominent  as  the  median  lobe,  subcrescentiform  in  outline.  Dorsal  fur- 
rows concave  inward,  about  as  deeply  impressed  as  the  glabellar  furrows. 
Fixed  cheeks  rather  broad  along  the  posterior  margin  of  the  head,  becom- 
ing rapidly  narrower  to  a  point  just  behind  the  palpebral  lobe;  the  palpe- 
bral  lobe  rather  prominent,  the  cheek  becoming  very  narrow  anteriorly. 
Occipital  furrow  and  occipital  segment  well  denned,  extending  across  the 
fixed  cheeks.  The  entire  surface  ornamented  with  small,  low,  rounded 
tubercles,  somewhat  variable  in  size.  Free  cheeks,  thorax  and  pygidium 
unknown." — Weller,  1903. 

The  above  description  by  Weller  is  the  most  detailed  that  has  so  far  been 
published,  and  as  the  specimens  now  under  study  show  no  additional 
features  both  his  description  and  figures  are  reproduced. 

Occurrence. — MARTINSBURG  SHALE  (Sinuites  bed).  Carlisle  and 
Chambersburg,  Pennsylvania,  and  Strasburg,  Virginia. 

Collection. — U.  S.  National  Museum. 

Family    ODONTOPLEURIDAE 
Genus  AGIDASPIS  Murchison 
ACIDASPIS  TTLKICHI  n.  sp. 

Plate  XXXVII,  Figs.  6-8 

Description. — The  most  interesting  species  in  the  fauna  of  the  Fred- 
erick limestone  is  a  remarkably  spinose  trilobite  represented  by  rather 
numerous  fragments  of  the  free  cheek  with  its  extended  genal  spine. 
Unlike  most  American  species  of  Acidaspis  and  allied  genera,  the  spines 
on  the  free  cheek  of  the  present  one  continue  to  the  end  of  the  genal 
spine.  These  spines  are  regularly  and  closely  placed  and  are  of  consider- 
able length  along  the  free  cheek.  They  decrease  in  length  along  the  genal 
spine,  but  they  are  still  conspicuous  at  its  end.  Another  unusual  feature 
is  a  great  curvature  of  the  free  cheek  with  its  genal  spine,  apparently 
indicating  that  the  latter  were  directed  over  the  thorax  of  the  trilobite. 


356  SYSTEMATIC  PALEONTOLOGY 

The  general  aspect  of  this  trilobite  is  not  unlike  certain  European 
species  of  Acidaspis.  This  species  can  be  recognized  easily  from  its  free 
cheeks,  but  more  of  the  trilobite  is  necessary  before  its  affinities  can  be 
definitely  determined. 

The  specific  name  is  in  honor  of  Dr.  E.  0.  TJlrich  in  appreciation  of 
his  work  on  the  faunas  and  stratigraphy  of  the  Appalachian  Valley. 

Occurrence. — FREDERICK  LIMESTONE.    Frederick,  Maryland. 

Collections. — Maryland  Geological  Survey,  U.  S.  National  Museum. 

Order  PROPARIA 

Family  CALYJWENIDAE 

Genus  CALYMENE  Brongniart 

CALYMENE  GEANULOSA  (Foerste) 

Plate  LVI,  Figs.  1,  2 

Calymene  callicephala  granulosa  Foerste,  1909,  Bull.   Sci.   Lab.   Denison 
Univ.,  vol.  xiv,  p.  294. 

Description. — This  species  is  one  of  several  that  have  usually  been 
identified  as  Calymene  callicepliala,  but  the  latter  name  has  been  dropped 
on  account  of  uncertainty  as  to  the  species  represented.  The  Eden  form 
of  Calymene  differs  conspicuously  from  other  Cincinnatian  species  of  the 
genus  in  the  presence  of  numerous  granules  upon  the  carapace.  Other 
differences,  such  as  smaller  size  and  a  less  strongly  elevated  anterior  border 
of  the  cephalon,  may  be  noted,  but  the  granulose  surface  is  the  best  marked 
feature. 

Occurrence. — MARTINSBURG  SHALE  (Eden  division).  Jordans  Knob, 
one  and  one-half  miles  northeast  of  Fort  Loudon,  Pennsylvania ;  Cowans 
Gap,  five  miles  northeast  of  McConnellsburg ;  and  Tuscarora  Mountain, 
two  and  one-half  miles  southeast  of  McConnellsburg,  Pennsylvania; 
Eickard  Mountain,  Washington  County,  Maryland.  Eden  shale  at  Cin- 
cinnati, Ohio. 

Collections. — Maryland  Geological  Survey,  U.  S.  National  Museum. 


MARYLAND  GEOLOGICAL  SURVEY  357 

CALYMENE  SENARIA  Conrad 

Plate  LI,  Fig.  15 

Calymene  senaria  Conrad,   1841,   5th   Ann.  Kept.   Geol.   Surv.   New  York, 

pp.  38,  49. 

Calymene  senaria  Hall,  1847,  Pal.  New  York,  vol.  i,  p.  238,  pi.  64,  figs.  3a-n. 
Calymene  senaria  Weller,  1903,  Geol.  Surv.  New  Jersey,  Pal.,  vol.  iii,  p.  203, 

pi.  xv,  fig.  23. 

Description. — "  Head  sub-semicircular  or  sublimate  in  outline,  the 
anterior  and  lateral  margins  being  more  or  less  nearly  regularly  rounded, 
and  the  posterior  broadly  sinuous,  with  the  posterior  lateral  extremities 
bluntly  subangular  or  abruptly  rounded.  Free  cheeks  irregularly  tri- 
angular in  outline,  with  thick,  rounded,  lateral  margins,  denned  by  a 
distinct,  rounded  marginal  furrow,  which  is  continuous  with  the  furrow 
separating  the  anterior  end  of  the  glabella  from  the  prominent,  elevated, 
anterior  margin  of  the  head.  Facial  sutures  originating  just  in  front  of 
the  genal  angles,  passing  obliquely  forward  and  inward  for  a  little  more 
than  half  the  distance  to  the  eyes,  then  curving  inward  to  the  base  of 
the  eye-lobe,  and  after  passing  around  the  eyes,  extending  forward  and 
intersecting  the  anterior  margin  at  points  a  little  nearer  together  than  the 
breadth  between  the  eyes.  Eyes  small  and  rather  prominent.'  Glabella  more 
prominent  than  the  cheeks  and  separated  from  them  by  deep,  dorsal  fur- 
rows, about  as  wide  behind  as  its  length,  including  the  occipital  segment, 
much  narrower  in  front;  the  frontal  and  three  pairs  of  lateral  glabellar 
lobes  separated  by  three  pairs  of  glabellar  furrows,  of  which  the  anterior 
pair  is  much  the  faintest  and  shortest;  each  member  of  the  second  pair 
extends  about  one-fourth  the  distance  across  the  glabella,  slightly  curved 
posteriorly,  the  posterior  pair  deeper  and  wider  than  either  of  the  others, 
each  member  extending  about  one-third  the  distance  across  the  glabella 
and  directed  obliquely  backward.  Occipital  furrow  deep  and  prominent, 
connecting  with  the  dorsal  furrows  and  less  conspicuously  with  the  mar- 
ginal furrows  of  the  posterior  margin  of  the  fixed  cheeks,  arching  slightly 
forward  at  the  middle  of  the  glabella.  Occipital  segment  well  defined, 
arching  a  little  forward,  about  as  high  as  the  most  prominent  portion  of 
the  glabella  in  front.  Fixed  cheeks  convex,  provided  with  a  deep,  broad 
furrow  along  their  posterior  margin. 


358  •  SYSTEMATIC  PALEONTOLOGY 

"  Pygidium  wider  than  long,  more  or  less  subtrigonal  in  outline,  but 
with  the  anterior  margin  broadly  rounded.  Axis  well  defined,  convex, 
extending  nearly  to  the  posterior  margin,  with  five  or  six  transverse  seg- 
ments, which  grow  fainter  posteriorly.  The  pleurae  convex,  each  with 
about  five  segments,  which  are  furrowed  distally.  Whole  surface  of  the 
test  minutely  granular." — Weller,  1903. 

The  fragments  of  this  species  noted  in  the  basal  part  of  the  Martins- 
burg  shale  agree  in  all  characters  with  the  New  Jersey  Trenton  specimens 
described  in  detail  by  Weller  as  above. 

Occurrence. — MARTINSBURG  SHALE  (Sinuites  bed).  Chambersburg, 
Pennsylvania,  and  Strasburg,  Virginia. 

Collections. — Maryland  Geological  Survey,  U.  S.  National  Museum. 

Family  CHEIRURIDAE 

Genus  GERAURUS  Green 

CERAURUS  PLEUREXANTHEMUS  Green 

Plate  XLIII,  Figs.  22,  23 

Ceraurus  pleurexanthemus  Green,  1832,  Monthly  Amer.  Jour.  Geol.,  vol.  1, 

p.  560,  pi.  iv,  fig.  10. 
Ceraurus  pleurexanthemus  Green,  1832,  Mono.  Trilobites  North  America, 

p.  84,  text  fig.  10,  cast  33. 
Ceraurus  pleurexanthemus  Hall,  1847,  Pal.  New  York,  vol.  i,  p.  242,  pi.  Ixv, 

figs,  la-c,  le-g. 
Ceraurus   pleurexanthemus  Weller,   1903,   Geol.   Surv.   New  Jersey,   Pal., 

vol.  iii,  p.  204,  pi.  xv,  fig.  28. 
Ceraurus  pleurexanthemus  Raymond  and  Benton,  1913,  Bull.  Mus.  Comp. 

Zool.,  vol.  liv,  p.  528,  pi.  i,  fig.  1;  pi.  ii,  figs.  1,  2,  7. 

Description. — "  Head  crescentif orm  in  outline,  with  the  posterior 
lateral  angles  extended  into  long,  curved,  genal  spines,  which  are  attached 
to  the  fixed  cheeks.  Free  cheeks  irregularly  triangular  in  outline,  the 
eyes  small.  Facial  suture  starting  at  the  lateral  margin,  and  after 
extending  inward  toward  the  glabella,  making  a  sharp  turn  forward  just 
back  .of  the  eye,  and  after  passing  around  the  eye,  curving  gently  for- 
ward, cutting  the  anterior  margin  of  the  head  in  front  of  the  glabella. 
Glabella  prominent,  convex,  broadest  in  front,  extending  nearly  to  the 


MARYLAND  GEOLOGICAL  SURVEY  359 

anterior  margin  of  the  head.  Glabellar  furrows  well  defined,  but  not 
extending  across  the  glabella.  The  two  anterior  pairs  straight,  each 
portion  extending  over  about  one-fourth  the  width  of  the  glabella.  The 
third  pair  extending  inward  about  as  far  as  the  other  two,  and  then 
bending  abruptly  backward  and  joining  the  occipital  furrow,  leaving  the 
posterior  glabellar  lobes  more  or  less  detached.  Occipital  furrow  deep 
and  well  defined,  arching  a  little  forward  upon  the  glabella  extended 
laterally  upon  the  fixed  cheeks  nearly  to  the  lateral  margins,  where  it 
joins  a  marginal  furrow  just  in  front  of  the  genal  spine,  which  passes 
anteriorly.  Occipital  segment  well  defined.  Dorsal  furrow  rather  sharply 
impressed.  Fixed  cheeks  convex,  their  posterior  lateral  angles  extended 
into  prominent,  curved,  genal  spines.  Whole  surface  of  the  head,  except 
the  dorsal,  glabellar,  occipital  and  marginal  furrows,  strongly  granulose 
or  papillose,  with  some  scattered  tubercles  larger  than  the  others." — 
Weller,  1903. 

The  above  description  by  Weller  applies  in  detail  to  the  characters  of 
the  head  fragments  found  in  the  Chambersburg  limestone.  Several 
species  have  been  confused  under  the  name  of  Ceraurus  pleurexanthemus 
and  better  material  may  show  the  Chambersburg  limestone  specimens  to 
be  incorrectly  referred  here. 

Occurrence. — CHAMBERSBURG  LIMESTONE  ( Caryocystites  bed).  Fort 
Loudon,  Franklin  County,  Pennsylvania.  Black  Eiver  of  New  York, 
Canada,  etc. 

Collections. — Maryland  Geological  Survey,  TJ.  S.  National  Museum. 

Genus  PLIOMEROPS   Raymond 

PLIOMEROPS  SALTERI  (Billings) 

Plate  XXXVI,  Fig.  13 

Amphion  salteri  Billings,  1861,  Canadian  Nat.  and  Geol.,  p.  322,  text  fig.  6. 
AmpMon  salteri  Billings,  1865,  Pal.  Foss.,  vol.  i,  Geol.  Surv.  Canada,  p.  352, 
text  fig.  339. 

Description. — Pygidium  small,  about  6  mm.  long  and  10  mm.  wide  at 
the  base.  Glabella  convex,  oblong,  one-third  the  width  of  the  head,  with 


360  SYSTEMATIC  PALEONTOLOGY 

straight  sides  and  a  narrow  margin  in  front;  neck  furrow  extending 
entirely  across;  three  pairs  of  glabellar  furrows  directed  slightly  back- 
ward, their  inner  extremities  separated  by  about  one-third  the  width  of 
the  glabella.  Fixed  cheeks  covered  with  small  tubercles  and  separated 
from  the  glabella  by  a  deep  groove  on  each  side. 

Pygidium  6  mm.  long  and  about  the  same  at  its  greatest  width ;  front 
margin  rounded  and  the  posterior  somewhat  straight.  Axis  conical  and 
strongly  convex  with  five  or  six  well-defined  segments.  Pleurae  of  the 
pygidium  five  on  each  side  and  nearly  parallel  with  the  axis  in  their 
posterior  half,  then  curving  inward  to  join  the  axial  segments. 

Identified  somewhat  doubtfully  in  the  Middle  Beekmantown  (Cera- 
topea  zone)  in  the  Appalachian  Valley  of  Maryland  and  southern  Penn- 
sylvania. Imperfect  pygidia  with  the  characteristic  pleurae  were  observed 
in  exposures  along  the  Cumberland  Valle}r  Kailroad  northeast  and  south- 
east of  Halfway,  Maryland. 

Occurrence. — BEEKMANTOWN  LIMESTONE  (Ceratopea  zone) .  Halfway, 
Maryland. 

Collection. — IT.  S.  National  Museum. 

Family  PHACOPIDAE 

Genus  PTERYGOMETOPUS  Schmidt 

PTEKYGOMETOPUS  CALLICEPHALUS  (Hall) 

Plate  XLIII,  Figs.  18-21 

Phacops  callicephalus  Hall,  1847,  Pal.  New  York,  vol.   i,  p.  247,  pi.  Ixv, 

figs.  3a-l. 
Pterygometopus  callicephalus  Clarke,  1894,  Geol.  Minnesota,  vol.  iii,  pt.  2, 

p.  731,  text  figs.  51,  52;  p.  732. 
Pterygometopus  callicephalus  Weller,  1903,  Geol.  Surv.  New  Jersey,  Pal., 

vol.  iii,  p.  206,  pi.  xv,  figs.  29-32. 

Description. — "  Head  sublimate  in  outline,  obtusely  subangular  in 
front,  genal  angles  broad  and  rounded,  with  no  indication  of  spinules. 
Glabella  large,  depressed-convex,  broad  and  rounded  in  front,  becoming 
much  narrower  behind;  frontal  lobe  large,  subelliptical  in  outline; 


MARYLAND  GEOLOGICAL  SURVEY  361 

anterior  pair  of  glabellar  furrows  starting  from  opposite  the  anterior 
extremities  of  the  eyes,  directed  obliquely  backward  and  each  one  extend- 
ing over  a  little  more  than  one-third  the  width  of  the  glabella;  second  pair 
of  glabellar  furrows  shorter  and  a  little  shallower  than  the  first,  directed 
obliquely  forward;  third  pair  of  glabellar  furrows  directed  toward  the 
axis  of  the  glabella  for  a  short  distance  and  then  bending  abruptly  back- 
ward and  joining  the  occipital  furrow,  leaving  the  small,  basal  glabellar 
lobes  wholly  detached.  Occipital  furrow  rather  deep  and  broad.  Occipital 
segment  rather  broad,  its  elevation  about  even  with  the  glabella  in  front, 
its  posterior  margin  convex.  Palpebral  lobes  prominent,  their  elevation 
being  nearly  that  of  the  glabella,  separated  from  the  glabella  by  the  deep 
dorsal  furrow,  and  marked  by  a  conspicuous  furrow  just  within  the 
border  of  the  eye.  Eyes  large,  lunate,  their  inner  margins  elevated  nearly 
or  quite  to  the  height  of  the  glabella,  their  anterior  ends  opposite  the  first 
glabellar  furrows  and  their  posterior  ends  reaching  nearly  to  the  occipital 
furrow.  Cheeks,  outside  the  eyes,  sloping  rather  abruptly  to  the  lateral 
margins  of  the  head ;  marked  along  the  posterior  margins  to  a  point  about 
one-half  the  distance  from  the  eye  to  the  margin  by  the  narrow,  but  rather 
sharply  impressed,  occipital  furrow,  whose  distal  extremity  is  rather 
abrupt;  the  lateral  borders  marked  by  an  ill-defined  marginal  furrow, 
which  originates  at  the  outer  extremity  of  occipital  furrow,  and  after 
passing  forward  nearly  parallel  with  the  margin,  joins  the  dorsal  furrow 
just  in  front  of  the  eye. 

"  Pygidium  subtriangular  in  outline,  rather  abruptly  rounded  or  sub- 
angular  posteriorly.  Axis  prominent,  but  rather  narrow,  its  margin 
slightly  incurved  and  abruptly  rounded  behind,  marked  by  from  eight  to 
ten  somewhat  sinuous  annulations ;  the  pleurae  slightly  flattened  adjacent 
to  the  axis,  but  soon  curving  rather  abruptly  to  the  lateral  margins, 
marked  by  about  six  grooved  segments,  with  slight  traces  of  others 
posteriorly. 

"  Surface  of  the  glabella,  palpebral  lobes,  occipital  segment  and  cheeks 
inside  the  marginal  furrow  distinctly  pustulose,  the  little  tubercles  being 
more  or  less  irregular  in  size;  upon  the  cheeks  outside  the  border  of  the 


362  SYSTEMATIC  PALEONTOLOGY 

eyes  the  papillae  are  much  less  conspicuous  than  upon  the  glabella  and 
the  marginal  border  is  perfectly  smooth.  Pygidium  unornamented, 
except  by  the  grooves  marking  the  segments,  which  do  not  extend  entirely 
to  the  border,  thus  leaving  a  plain,  perfectly  smooth,  narrow  marginal 
border."— Weller,  1903. 

Occurrence. — CHAMBERSBURG  LIMESTONE  (Tetradium  cellulosum  bed) . 
Several  localities  south  of  Chambersburg,  Pennsylvania.  This  species 
has  hitherto  been  supposed  to  be  restricted  to  the  Trenton  rocks  of  the 
United  States  and  Canada. 

Collection. — U.  S.  National  Museum. 

subclass  EUCRUSTACEA 

Superorder    BRANCHIOPODA 

Order  NOTOSTRACA 

Genus  RIBEIRIA    Sharpe 

RlBEIRIA  ?  NUCULITIFORMIS  Cleland 

Plate  XXXI,  Figs.  13,  14 

Ribeiria  f  nuculitiformis  Cleland,  1900,  Bull.  Amer.  Pal.,  vol.  lii,  p.  133 
(261),  pi.  xvi,  figs.  10-14. 

Description. — Shell  small,  varying  from  1.5  mm.  by  3  mm.  to  6  mm. 
by  12  mm.,  compressed  laterally,  with  the  dorsal  margin  concave  and  the 
sides  convex.  In  casts,  a  deep  notch  about  one-fourth  the  length  of  the 
shell  is  shown  just  below  the  beak  and  extends  obliquely  towards  the 
middle  of  the  ventral  side. 

The  shell  of  this  interesting  crustacean  much  resembles  a  species  of  the 
pelecypod  genus  Nuculites,  whence  the  specific  name. 

Occurrence. — BEEKMANTOWN  LIMESTONE  (Stonehenge  member). 
Hagerstown,  Maryland.  An  extremely  abundant  fossil  in  the  Tribes  Hill 
limestone  at  Fort  Hunter,  New  York. 

Collection. — U.  S.  National  Museum. 


MARYLAND  GEOLOGICAL  SURVEY  363 

Superorder  OSTRACODA 
Family  LEPERDITIIDAE 

Genus  ISOGHILIXA  Jones 
ISOCHILINA  GREGARIA    (Whitfield) 

Plate  XXXVI,  Figs.  10-12 

Primitia  gregaria  Whitfield,  1889,  Bull.  Amer.  Mus.  Nat.  Hist.,  vol.  ii,  p.  58, 

pi.  xiii,  figs.  3-5. 
Isochilina  gregaria  Jones,  1890,  Quart.  Jour.  Geol.  Soc.  London,  vol.  xlvi, 

p.  22,  pi.  i,  figs.  9,  10. 
Isochilina  amiana'  Ulrich,  1891,  Jour.  Cincinnati  Soc.  Nat.  Hist.,  vol.  xiii, 

pt.  1,  p.  180,  pi.  xi,  figs.  12a-c. 
Isochilina  Ottawa  var.  intermedia  Jones,  1891,  Cont.  Micro-Pal.,  Geol.  Surv. 

Canada,  pt.  3,  p.  66,  pi.  x,  figs.  10,  11. 

Description. — Carapace  about  4  mm.  long,  obliquely  oval  in  form; 
hinge  line  straight,  in  length  about  three-fifths  that  of  the  valves.  Sur- 
face of  valves  convex,  most  elevated  across  the  narrow  end.  Sulcus 
poorly  defined,  broadly  triangular  extending  from  about  the  middle  of  the 
valve  to  the  hinge.  Surface  of  valves  marked  by  numerous  widely  spaced 
pits.  On  each  side  of  the  sulcus  there  is  usually  a  well-defined  node  or 
tubercle  and  often  one  is  at  its  lower  extremity. 

A  species  of  similar  size  and  shape  and  with  the  surface  markings  of 
the  Vermont  type  specimens  occurs  in  poor  preservation,  but  sometimes 
in  abundance  on  the  weathered  limestone  surfaces  of  the  Middle  Beek- 
mantown  of  Pennsylvania  and  Maryland. 

Occurrence. — BEEKMANTOWST  LIMESTONE  (Ceratopea  zone).  Several 
of  the  outcrops  along  the  National  Highway  west  of  Hagerstown  and  the 
turnpike  to  Williamsport,  Maryland. 

Collections. — Maryland  Geological  Survey,  U.  S.  National  Museum. 

ISOCHILINA  SEEYLI  (Whitfield) 
Plate  XXXV,  Fig.  12 

Primitia  seelyi  Whitfield,  1889,  Bull.  Amer.  Nat.  Hist,  vol.  ii,  p.  60,  pi.  xiii, 

figs.  6,  7. 
Isochilina  seelyi  Jones,  1890,   Quart.  Jour.   Geol.   Soc.  London,  vol.  xlvi, 

p.  22,  pi.  i,  fig.  7. 


364  SYSTEMATIC  PALEONTOLOGY 

Description. — Valves  about  4  mm.  in  length,  and  not  quite  3  mm.  long, 
with  the  straight  or  dorsal  margin  a  trifle  more  than  three-fifths  of  the 
entire  length.  Valves  convex,  and  wider  at  the  posterior  end;  cardinal 
angles  distinct.  Anterior  and  posterior  ends  with  flattened  margin, 
narrowing  along  the  basal  border  and  disappearing  along  the  mid-ventral 
edge.  Surface  covered  with  moderately  large,  depressed  pits,  most  of 
which  have  an  elevated  granule  in  the  center.  A  nearly  circular,  smooth 
spot,  and  above  it  a  rapidly  widening  area  also  without  pits,  extending  to 
the  dorsal  border,  replaces  the  usual  sulcus  or  tubercles  of  the  surface 
of  such  ostracoda. 

The  surface  punctae  and  the  smooth  spot  in  the  anterodorsal  part  of 
the  valve  easily  distinguish  this  species.  The  types  were  found  in  the 
Beekmantown  limestone  at  Shoreham,  Vermont. 

Occurrence. — BEEKMANTOWN  LIMESTONE  (Turritoma  zone).  Huyett, 
Maryland. 

Collections. — Maryland  Geological  Survey,  U.  S.  National  Museum. 

Genus  LEPERDITIA    Rouault 

LEPERDITIA  FABULITES  (Conrad) 

Plate  XXXIX,  Fig.  1C;  Plate  XLIII,  Figs.  1-5 

Cytherina  fabulites  Conrad,  1843,  Proc.  Acad.  Nat.  Sci.  Philadelphia,  vol.  i, 

p.  332. 
Leperditia  fabulites  Ulrich,  1891,  Jour.  Cincinnati  Soc.  Nat.  Hist.,  vol.  xiii, 

p.  173,  pi.  xi,  figs,  la-d,  2. 
Leperditia  fabulites  Ulrich,  1894,  Geol.  Minnesota,  vol.  iii,  pt.  2,  p.  634, 

pi.  xliii,  figs.  1-14. 
Leperditia  fabulites  Weller,  1903,  Geol.  Surv.  New  Jersey,  Pal.,  vol.  iii, 

p.  208,  pi.  xiii,  figs.  11,  12. 

Description. — "  Carapace  of  medium  size,  obliquely  subovate,  compara- 
tively long,  widest  posteriorly;  ventral  curves  moderate,  strongest  just 
behind  the  mid-length ;  cardinal  line  straight,  comparing  with  the  length 
of  the  valve  as  two  is  to  three,  the  two  extremities  almost  equally  angular ; 
hight  of  ends  about  as  three  is  to  four,  both  obliquely  truncate  above,  the 
anterior  narrowly  rounded  in  the  middle;  the  posterior  outline  more 


MARYLAND  GEOLOGICAL  SURVEY  365 

broadly  and  evenly  curved  though  having  the  usual  backward  swing. 
Ventral  edge  of  carapace  obtuse,  scarcely  flattened,  with  a  slight  furrow 
on  each  side  near  the  edge  of  the  right  valve  in  which  a  row  of  minute 
punctae  is  generally  distinguishable;  overlap  extending  all  around  the 
free  edges,  strongest  ventrally ;  except  in  rare  instances,  neither  valve  has 
a  flange  or  flattened  border,  and  when  present  it  is  in  all  cases  very 
narrow  and  undefined ;  dorsal  edge  somewhat  thickened,  especially  upon 
the  left  side.  Surface  of  the  valves  smooth  or  very  faintly  pitted,  rather 
evenly  convex  with  the  greatest  thickness  somewhat  beneath  the  center; 
a  low  ridge-like  thickening  along  the  posterior  half  of  the  dorsal  margin 
of  the  left  valve  is  to  be  noticed.  Eye  tubercle  just  distinguishable  in 
most  cases,  rarely  so  distinct  as  in  the  specimen  figured,  often  not  to  be 
detected.  On  the  inner  surface,  however,  it  is  always  marked  by  a  dis- 
tinct pit.  Muscle  spot  not  distinguishable  externally  except  when  the 
specimens  are  weathered,  but  on  the  inner  side  it  is  often  well  marked 
and  surrounded  by  fine  reticulating  radial  lines,  short  dorsally,  longest 
post-ventrally.  On  the  inner  side  of  the  ventral  edge  of  the  right  valve 
there  are  two  rows  of  small  papillae,  three  to  five  in  each,  the  number 
seeming  to  increase  with  age.  The  purpose  of  these  papillae,  one  series 
of  which  occurs  in  the  anterior  third,  the  other  in  the  posterior  evidently 
was  to  prevent  undue  overlapping  of  the  valves  by  presenting  an  obstacle 
to  the  entering  ventral  edge  of  the  left  valve." — Ulrich,  1894. 

Although  this  species  has  been  cited  as  a  wide-spread  characteristic 
fossil  of  both  the  Stones  Elver  and  Black  Eiver  groups,  the  typical  form 
is  really  restricted  to  the  latter  rocks.  The  original  types  were  described 
from,  the  Platteville  limestone  of  Wisconsin,  the  equivalent  of  the  Low- 
ville  limestone  of  more  eastern  localities. 

Occurrence.— -CHAMBERSBTJRG  LIMESTONE  (Tetradium  cellulosum  bed) . 
Fort  London  and  other  localities  in  Franklin  County,  Pennsylvania. 
STONES  EIVER  LIMESTONE.  Pinesburg  and  Wilson,  Maryland. 

Collections. — Maryland  Geological  Survey,  U.  S.  National  Museum. 


366  SYSTEMATIC  PALEONTOLOGY 

Genus  LEPERDITELLA  Ulrich 

LEPERDITELLA  TUMIDA  (Ulrich) 

Plate  XLIII,  Figs.  10-12 

Leperditia  tumida  Ulrich,  1892,  Amer.  Geol.,  vol.  x,  p.  264,  pi.  ix,  figs.  1-3. 
Leperditella  tumida  Ulrich,  1894,  Geol.  Minnesota,  vol.  iii,  pt.  2,  p.  636. 

Description. — Valves  ovate,  leperditoid,  with  a  straight  back,  rather 
short,  with  the  posterior  end  widest,  tumid,  the  convexity  of  the  surface, 
except  for  a  slight  flattening  and  lengthening  of  the  dorsal  and  anterior 
slopes,  nearly  uniform.  Surface  obscurely  punctate,  otherwise  smooth, 
there  being  no  external  signs  of  either  the  eye-tubercle  or  muscle  spot. 
Right  valve  a  little  smaller  than  the  left  and  fitting  into  a  groove  in  it. 

Length  of  a  large  right  valve,  2.6  mm. ;  height,  1.82  mm. ;  thickness, 
0.75  mm. 

This  is  one  of  the  characteristic  microscopic  fossils  of  the  Lowville 
limestone  in  the  Ohio  and  Appalachian  valleys. 

Occurrence. — CHAMBEKSBURG  LIMESTONE  (Tetradium  cellulosum 
bed).  Fort  London  and  other  localities  in  Franklin  County,  Pennsyl- 
vania. 

Collections. — Maryland  Geological  Survey,  TL  S.  National  Museum. 

Genus  APARCHITES  Jones 

APAKCHITES  MINUTISSIMUS  (Hall) 

Plate  LV,  Fig.  33 

Leperditia  (Isochilina')  minutissima  Hall,  1872,  24th  Rep.  New  York  State 
Cab.  Nat.  Hist,  p.  231,  pi.  viii,  fig.  13  (advance  sheets,  1871,  p.  7). 

Leperditia  (Isochilina)  minutissima  Hall  and  Whitfield,  1875,  Geol.  Surv. 
Ohio,  Pal.,  vol.  ii,  p.  102,  pi.  iv,  fig.  4. 

Aparchites  minutissimus  Ulrich,  1889,  Geol.  Surv.  Canada,  Cont.  Micro.-Pal., 
pt.  2,  p.  49,  pi.  ix,  fig.  5. 

Description. — •"  Carapace  minute,  less  than  two-hundredths  of  an  inch 
in  length,  the  width  being  about  two-thirds  the  length,  greatest  at  the 
anterior  third,  giving  a  broadly  ovate  outline,  with  a  straight  cardinal 
margin  of  about  two-thirds  the  length  of  the  valve. 


MARYLAND  GEOLOGICAL  SURVEY  367 

"  Surface  of  the  valves  smooth,  rising  into  an  obtusely  pointed  promi- 
nence at  the  anterior  third  of  the  length ;  basal  margins  of  the  valves  not 
overlapping,  so  far  as  can  be  ascertained/' — Hall  and  Whitfield,  1875. 

This  minute  o^tracod  may  be  readily  recognized  .by  its  Leper ditia-l&Q 
carapace  with  non-overlapping  valves,  the  surface  of  which  is  smooth 
and  rises  into  an  obtuse  prominence.  An  abundant  fossil  in  the  Cin- 
cinnatian  rocks  of  the  Ohio  Valley,  particularly  in  the  Eden  shale. 

Occurrence. — MARTINSBUEG  SHALE  (Eden  division).  Jordans  Knob, 
one  and  one-half  miles  northeast  of  Fort  Loudon,  Pennsylvania,  and  debris 
on  the  west  slope  of  Eickard  Mountain,  Washington  County,  Maryland. 

Collection. — U.  S.  National  Museum. 

Family    BEYRICHIIDAE 

Genus  DREPANELLA  Ulrich 

DREPANELLA  MACRA  Ulrich 

Plate  XLIII,  Pigs.  13-15 

Drepanella  macer  Ulrich,  1894,  Jour.  Cincinnati  Soc.  Nat.  Hist,  vol.  xiii, 

p.  119,  pi.  viii,  figs.  4a-c. 
Drepanella  macro,  Ulrich  and  Bassler,  1908,  Proc.  U.  S.  Nat.  Mus.,  vol.  xxxv, 

p.  291,  fig.  17,  pi.  xli,  figs.  12-14. 

Description. — "  Valves  subquadrate,  about  2.0  mm.  long  and  1.25  mm, 
high,  with  the  body  very  thin  and  shallow,  the  thickness  of  the  entire 
carapace  at  a  point  near  the  middle  being  only  about  0.3  mm.  Ventral 
margin  straight  or  sinuate ;  ends  subequal,  the  posterior  a  little  the  most 
curved;  postero  and  antero-dorsal  regions  angular,  the  angles  10  or  15 
degrees  greater  than  a  right  angle.  Ventral  edge  slightly  thickened. 
Marginal  or  sickle-shaped  ridge  high,  projecting  beyond  the  dorsal  edge, 
running  parallel  with  and  very  close  to  the  abrupt  posterior  margin ;  then 
curving  more  rapidly  than  does  the  outline  of  the  valve  into  the  ventral 
margin,  it  gradually  increases  its  distance  from  the  ventral  edge,  and  in  a 
slightly  flexuous  manner  traverses  the  valve  for  almost  its  entire 
length,  terminating  at  a  point  near  the  middle  of  the  anterior  margin. 
Postero-median  ridge  consisting  of  three  prominently  confluent  nodes,  the 

24 


3G8  SYSTEMATIC  PALEONTOLOGY 

uppermost  projecting  considerably  beyond  the  dorsal  margin.  Antero- 
median  node  large,  prominent  and  of  triangular  form.  Antero-dorsal  node 
projecting  prominently  beyond  the  edge,  but  not  as  high,  and  only  about 
half  as  large  as  the  antero-median  one." — Ulrich,  1894. 

The  types  of  this  striking  ostracod  were  found  in  the  topmost  division 
(Lebanon)  of  the  Stones  River  limestone  of  Central  Tennessee. 

Occurrence. — CHAMBERSBURG  LIMESTONE  (Tetradium  cellulosum 
bed) .  Fort  Loudon,  Pennsylvania. 

Collections. — Maryland  Geological  Survey,  U.  S.  National  Museum. 

Genus  MAGRONOTELLA  Ulrich 

MACRONOTELLA  ULRICHI  Euedemann 

Plate  XLIII,  Figs.  6-9 

Macronotella  ulrichi  Ruedemann,  1901,  New  York  State  Mus.  Bull.,  No.  49, 
p.  83,  pi.  vi,  figs.  6-16;  pi.  vii,  fig.  1. 

Description. — "  Valves  three-fourths  circular  to  subovate ;  dorsal  out- 
line rarely  straight,  mostly  prominent  in  the  central  part,  specially  in 
older  specimens;  cardinal  angles  obtusely  rounded  to  shortly  truncate; 
posterior  margin  with  a  little  longer  truncation,  lateral  and  ventral 
margins  forming  approximately  a  continuous  circular  line;  in  larger 
specimens  the  anterior  and  posterior  margins  more  strongly  rounded,  and 
the  ventral  margin  less  curved;  free  edges  in  most  specimens  with  a 
broad  depressed  border  and  beveled  edge.  Surface  strongly  convex, 
culminating  in  the  dorsocentral  region ;  in  some  specimens  almost  smooth, 
with  only  faint,  widely  and  irregularly  distributed  circular  impressions ; 
others  with  very  large  deep  pits;  on  the  apex  always  a  flat,  smooth 
circular  area.  Valve  projecting  slightly  above  the  straight  cardinal  line,  , 
and  forming  a  broad,  low,  triangular,  reentrant  cardinal  area. 

"  Dimensions :  Length,  2.7  mm. ;  height,  2.1  mm. ;  thickness,  .7  mm." — 
Euedemann,  1901. 

This  fine  ostracod  is  easily  distinguished  by  its  strongly  convex  valves 
with  a  flat,  smooth  area  at  the  apex  of  the  surface  which  elsewhere  is 
marked  by  circular  impressions  or  deep  pits. 


MARYLAND  GEOLOGICAL  SURVEY  369 

Occurrence. — CHAMBERSBURG  LIMESTONE  (Tetradium  cellulosum 
bed) .  Fort  Loudon,  Franklin  County,  Pennsylvania.  The  type  specimens 
were  found  in  the  Eysedorph  conglomerate  at  Eysedorph  Hill,  Eensselaer 
County,  New  York. 

Collection. — U.  S.  National  Museum. 

Genus  CERATOPSIS   Ulrich 

CERATOPSIS  CHAMBERSI  (Miller) 

Plate  LV,  Fig.  34 

Beyrichia  chambersi  Miller,  1874,  Cincinnati  Quart.  Jour.  Sci.,  vol.  i,  p.  234, 

fig.  27. 
Beyrichia  cham'bersi  Hall  and  Whitfleld,  1875,  Pal.  Ohio,  vol.  ii,  p.  104, 

pi.  iv,  figs.  11,  12. 
Ceratopsis  cham'bersi  Ulrich,  1894,  Geol.  Minnesota,  vol.  iii,  pt.  2,  p.  676, 

pi.  xlvii,  figs.  19-22. 

Description. — "  Carapace  minute,  the  extreme  length  not  exceeding 
half  a  line,  and  the  greatest  width  not  more  than  two-thirds  as  much  as 
the  length.  Form  of  the  valves  broad  ovate,  with  one  side,  for  a  space 
equal  to  about  one-fourth  of  the  width  of  the  figure,  cut  away,  forming 
the  straight  hinge-line,  which  is  equal  in  length  to  about  six-sevenths  of 
the  entire  length  of  the  carapace.  Greatest  width  of  the  valve  a  little 
more  than  one-third  of  the  length  from  the  anterior  end.  Surface  of  the 
valves  highly  convex,  most  prominent  near  the  middle  of  the  length, 
crossed  by  three  curving  sulci,  none  of  which  reach  the  ventral  border, 
the  middle  of  the  curve  being  directed  towards  the  posterior  extremity. 
The  middle  sulcus  is  stronger  and  much  deeper  than  the  others,  while  the 
posterior  one  is  faintly  marked,  and  situated  at  about  the  posterior  third 
of  the  length.  The  anterior  sulcus  is  short,  comparatively  deep,  nearly 
semicircular,  and  situated  within  the  anterior  third  of  the  length,  and 
about  midway  between  the  cardinal  and  basal  borders.  From  the  anterior 
margin  of  this  depression,  or  between  it  and  the  anterior  border  of  the 
valve,  there  rises  a  strong,  thickened,  lanceolate,  or  scythe-shaped,  curved 
spine,  which  equals  in  length  two-fifths,  or  sometimes  one-half  that  of 
the  entire  valve.  The  anterior  and  posterior  surfaces  of  the  spine  are 


370  SYSTEMATIC  PALEONTOLOGY 

convex,  the  latter  most  strongly  so,  while  the  lateral  edges  are  sharp  and 
the  ventral  one  generally  deeply  serrate,  although  a  few  specimens  have 
been  noticed  without  the  serrations,  perhaps  from  wearing.  The  margin 
of  the  valve  is  bordered  by  a  thickened  rim,  within  which  there  is  often  a 
slightly  depressed  channel.  Surface  of  the  crust  smooth,  or  very  finely 
granulose."— Hall  and  Whitfield,  1875. 

Occurrence. — MARTINSBURG  SHALE  (Eden  division).  Southern  Penn- 
sylvania and  on  the  west  slope  of  Rickard  Mountain  in  Maryland. 

Collections. — Maryland  Geological  Survey,  TL  S.  National  Museum. 

Genus  ULRICHIA  Jones 
ULRICHIA  BIVEETEX  (Ulrich) 
Plate  LY,  Fig.  32 

Leperditia  bivertex  Ulrich,  1879,  Jour.  Cincinnati  Soc.  Nat.  Hist.,  vol.  ii, 

p.  11,  pi.  vii,  figs.  5,  5a. 
Ulrichia  f  Uvertex  Ruedemann,  1912,  New  York  State  Mus.  Bull.,  No.  162, 

p.  120,  pi.  ix,  figs.  11,  12. 

Description. — •"  Length,  1.00  mm. ;  breadth,  .75  mm.  Carapace  minute, 
subrenif orm ;  dorsal  margin  straight,  over  two-thirds  as  long  as  the  entire 
length  of  the  valve;  anterior  and  posterior  extremities  equal  in  width; 
ventral  curve  nearly  uniform.  Valves  strongly  convex.  Tubercle  at  the 
anterior  end,  near  the  dorsal  margin  large,  rising  abruptly,  obtusely 
rounded,  and  slightly  directed  posteriorly.  Posterior  tubercle  situated 
near  the  dorsal  margin,  and  about  half  the  length  of  the  valve  from  the 
posterior  extremity,  less  obtusely  rounded,  and  more  prominent  than  the 
anterior  tubercle.  Between  the  tubercles  there  is  a  deep  sulcus,  extending 
from  the  dorsal  margin  to  one-half  the  distance  across  the  valve.  Surface 
smooth.  On  the  interior  there  is  a  corresponding  pit  for  each  tubercle, 
and  a  divisional  ridge  between  them." — Ulrich,  1879. 

Occurrence. — MARTINSSURG  SHALE  (Eden  division).  Jordans  Knob, 
one  and  one-half  miles  northeast  of  Fort  Loudon,  Pennsylvania. 

Collection. — U.  S.  National  Museum. 


MARYLAND  GEOLOGICAL  SURVEY  371 

Family  CYPRIDAE 

Genus  BYTHOGYPRIS   Brady 

BYTHOCYPEIS  CYLINDRICA  (Hall) 

Plate  LV,  Figs.  28-31;  Plate  LII,  Figs.  14-16 

Leperditia  (Isochilina)  cylindrica  Hall,  1872,  24th  Rep.  New  York  State 
Cab.  Nat.  Hist.,  p.  231,  pi.  viii,  fig.  12  (Extract  1871,  p.  7,  pi.  iv,  fig.  12). 

Bythocypris  cylindrica  Ulrich,  1894,  Geol.  Minnesota,  vol.  iii,  pt.  2,  p.  687, 
pi.  xliv,  figs.  29-35,  p.  688. 

Description. — "  Carapace  minute,  seldom  exceeding  two-hundredths  of 
an  inch  in  length,  nearly  twice  as  long  as  wide ;  valves  very  convex  and 
cylindrical,  the  anterior  and  posterior  ends  subequal  and  strongly 
rounded ;  cardinal  line  much  shorter  than  the  length  of  the  valve ;  tubercle 
obsolete.  Surface  smooth."— Hall,  1872. 

An  abundant  fossil  in  all  divisions  of  the  Trenton  and  Cincinnatian 
rocks  of  the  United  States  and  Canada. 

Occurrence. — MARTI:NTSBURG  SHALE  (Eden  division).  Southern  Penn- 
sylvania and  in  the  debris  from  the  same  on  Fairview  and  Eickard 
Mountains  in  Maryland. 

Collections. — Maryland  Geological  Survey,  TJ.  S.  National  Museum. 

Superorder    CIRRIPEDIA 
Family  LEP1DOCOLEIDAE    Clarke 

Genus  LEPIDOCOLEUS  Faber 
LEPIDOCOLEUS  JAMESI  (Hall  and  Whitfield) 
Plate  LV,  Figs.  1-4 ;  Plate  LII,  Figs.  24,  25 

Plumulites  jamesi  Hall  and  Whitfield,  1875,  Geol.  Surv.  Ohio,  Pal.,  vol.  ii, 

p.  106,  pi.  iv,  figs.  1-3. 
Lepidocoleus  jamesi  Faber,  1886,  Cincinnati  Soc.  Nat.  Hist.,  vol.  ix,  p.  15, 

pi.  i,  figs.  A-F. 
Lepidocoleus  jamesi  Ruedemann,   1901,  New  York   State   Museum   Bull., 

No.  42,  p.  521,  pi.  ii,  figs.  10-12. 

Description.-^"  General  form  of  the  plates  triangular,  with  the  apex  a 
little  inclined  to  one  side,  the  lateral  margins  gradually  and  rapidly  diverg- 
ing from  the  initial  point,  one  of  them  considerably  longer  than  the  other. 


372  SYSTEMATIC  PALEONTOLOGY 

Basal  margin  sigmoidal,  the  convex  portion  situated  next  to  the  longest 
lateral  face,  the  concave  portion  to  the  shorter,  and  the  shorter  lateral 
margin  deflected  downwards  in  some  cases  (probably  the  marginal  row 
of  plates ) . 

"  The  surface  of  the  plates  is  flattened  or  slightly  convex  on  the  sides, 
and  very  faintly  depressed  along  the  middle,  the  whole  marked  by  rather 
closely  arranged,  annulating,  and  scaliform  transverse  lines  parallel  with 
the  basal  or  sigmoidal  margin,  and  marking  stages  of  growth.  These 
transverse  lines  are  usually  faintest  near  the  apex,  and  gradually  increase 
in  width  with  the  increased  growth  of  the  plate,  but  in  some  cases  they 
are  quite  irregular  in  their  distances. 

"  The  length  from  the  apex  to  the  basal  margin  of  the  plate  is  usually  a 
little  greater  than  the  transverse  diameter,  and  seldom  exceeds  a  sixteenth 
of  an  inch,  the  largest  specimens  seen  not  measuring  a  line  in  their 
greatest  diameter/'— Hall  and  Whitfield,  1875. 

Occurrence. — MARTINSBUEG  SHALE  (Eden  division).  Jordans  Knob, 
one  and  one-half  miles,  northeast  of  Ft.  Lou  don;  Tuscarora  Mountain, 
two  and  one-half  miles  southeast  of  McConnellsburg,  Pennsylvania;  and 
in  sandstone  debris  on  the  east  slopes  of  Eickard  Mountain,  Washington 
County,  Maryland.  Also  in  the  Corynoides  bed  at  Williamsport, 
Maryland. 

Collections. — Maryland  Geological  Survey,  U.  S.  National  Museum. 

Superorder    MALACOSTRACA 

Division   PHYLLOCARIDA 

Family    CERATIOCARIDAE 

Genus  CARYOCARIS  Salter 

CAKYOCAEIS  SILICULA  n.  sp. 

Plate  LII,  Figs.  21-23 

Description. — Pod-shaped  bodies  which  have  been  identified  by  Salter 
as  the  carapace  of  phyllopods  under  the  name  of  Caryocaris,  are  known 
in  the  Canadian  shales  of  America,  but  no  more  recent  species  have  been 


.MARYLAND  GEOLOGICAL  SURVEY  373 

described.  The  discovery  of  well-preserved  examples  of  similar  phyllo- 
pods  in  considerable  numbers  in  the  lower  part  of  the  Martinsburg  shale 
just  above  the  Sinuites  zone  is  of  considerable  interest.  These  Middle 
Ordovician  phyllopods  all  conform  to  a  single  type  for  which  the  name 
Caryocaris  silicula  is  proposed.  The  species  differs  from  the  others  of  the 
genus  in  its  narrower  or  more  elongated  carapace,  and  a  more  nearly 
equal  anterior  and  posterior  extremity.  The  latter  characteristic  is  so 
marked  that  it  is  difficult  to  discriminate  the  two  extremities. 

A  complete  carapace  is  about  11  mm.  long  and  3.5  mm.  high.    No  other 
portions  of  the  organism  than  the  carapace  have  been  noted. 

Occurrence. — MARTINSBURG    SHALE    (Corynoides    bed).      Strasburg, 
Virginia,  and  in  the  same  zone  northward  to  Chambersburg,  Pennsyl- 
vania. 
I 

Collections. — Maryland  Geological  Survey,  IT.  S.  National  Museum. 


PLATE  XXIV 

PAGE 

OLENELLUS  THOMPSONI  (Hall) 339 

A  large,  almost  entire  individual  of  this  characteristic  trilobite  with 

the  third  segment  unusually  prolonged.     (After  Walcott.) 
Fragments  of  the  free  checks  or  of  the  segments  are  the  portions  most 
frequently  found  in  the  Antietam  Sandstone  of  Maryland. 
Cambrian.    Georgia  slate,  Parker's  quarry,  Georgia,  Vermont. 


374 


MARYLAND  GEOLOGICAL  SURVEY 


CAMBRIAN  AND  ORDOVICIAN,  PLATE  XXIV 


LOWER  CAMBRIAN  TRiLOBiTE  Olenellus  thompsoni  Hall. 


25 


PLATE  XXV 

PAGE 

Figs.  1-4.    OBOLLELA  MINOB  Walcott 233 

1.  Cast  of  pedicle  valve,  enlarged. 

2.  Exterior  of  pedicle  valve. 

3.  Exterior  of  brachial  valve. 

4.  Cast  of  interior  of  brachial  valve  and  edge  view  of  same. 

Cambrian  (Waucoban),  near  Stissingville,  Dutchess  County, 
New  York. 

Figs.  5-8.    HYOLITHES  COMMUNIS  Billings 318 

5.  6.  Lateral  views  of  two  specimens,  enlarged. 

7,  8.  Transverse  sections  showing  irregularities  in  thickness  of  shell. 
Cambrian  (Waucoban),  Troy,  New  York. 

Fig.  9.     SCOLITHUS  LINEABIS  Hiildemaiin 276 

Fragment  of  drifted  Antietam   Sandstone,  preserving  the  tubes  of 
this  species. 

Pebble,  five  miles  southwest  of  Washington,  D.  C. 
Figures  1  to  8  are  after  Walcott. 


375 


MARYLAND  GEOLOGICAL  SURVEY 


CAMBRIAN  AND  ORDOVICIAN,  PLATE  XXV 


I. 


LOWER  CAMBRIAN.      ANTIETAM  SANDSTONE  FOSSILS. 


PLATE  XXVI 

PAGE 

Fig.  1-9.    DOLICHOMETOPUS  n.  sp 338 

1.  A  cranidium  slightly  elongated  by  pressure  from  direction  indicated 

by  arrow.     X  3. 

2.  A  similar  but  less  distorted  cranidium.     X  3. 

3.  Rock  fragment  with  cranidium  of  nearly  normal  shape.     X  3. 

4.  A   large   cranidium   of  the   same  species.     Lateral   pressure   has 

narrowed  the  head.     X  1.5. 

5.  A  small  pygidium  of  normal  shape.    X  1.5. 

6.  A  large  pygidium  of  apparently  the  same  species,  slightly  distorted. 

X  1.5. 

7.  Very  small  undistorted  cranidium.    X  3. 

8.  Two  cranidia  of  normal  size.    The  upper  head  is  slightly  shortened 

while  the  lower  one  is  laterally  compressed  by  pressure  from 
the  direction  of  the  arrow,  making  it  appear  elongate.  X  3. 

9.  Three  well  preserved  cranidia  with  arrow  showing  direction  of 

pressure.  The  upper  left  hand  specimen  is  of  another  species 
with  broader  fixed  cheeks.  The  upper  of  the  two  speci- 
mens on  the  right  is  shortened  obliquely,  the  lower  one  antero- 
posteriorly.  X  3. 

Cambrian.     Elbrook  limestone  (20  feet  above  base).     Small 
quarry  on  eastern  outskirts  of  Waynesboro,  Pennsylvania. 


376 


MARYLAND  GEOLOGICAL  SURVEY 


CAMBRIAN  AND  ORDOVICIAN,  PLATE  XXVI 


8  9 

MIDDLE  CAMBRIAN.       ELBROOK  LIMESTONE  FOSSILS. 


PLATE  XXVII 

PAGE 

Figs.  1-5.    EOOBTHIS  DESMOPLEURA  (Meek) 237 

1.  Brachial  valve  enlarged. 

2.  Pedicle  valve,  with  characteristic  surface. 

3.  4.  Cast  of  pedicle  valve  and  side  outline  of  same. 

5.  Exterior  of  pedicle  valve  showing  surface  characters. 

Ordovician  (Ozarkian  ?),  El  Paso  County,  Colorado. 

Figs.  6-8.    SAUKIA  STOSEI  Walcott 351 

6.  Surface   of   limestone   with   cranidia,   free   cheek,   and   pygidium 

weathered  out  in  relief.    X  3. 

7.  Side  view  of  cranidium  and  free  cheek  shown  in  Fig.  6.    X  3. 

8.  Another  view  of  cranidium  and  free  cheek  shown  in  Fig.  6. 

Cambrian     (Ozarkian),    Conococheague    Is.,  near    Scotland, 
Franklin  County,  Pennsylvania. 

Fig.  9.    FOSSIL  BEEF-FORMING  CALCAREOUS  ALGAE 190 

Photograph  of  a  rock  mass  forming  the  edge  of  a  reef  of  fossil  algae 
(Cryptozoon)  overlapped  by  stratified  layers  of  the  argillaceous 
Conococheague  limestone.  This  algal  growth  developed  regular 
concentric  layers  in  its  lower  part  (A),  but  these  layers  or 
laminae  became  rather  loosely  interwoven  in  the  upper  portion 
(B).  In  the  upper  righthand  corner  (C)  the  overlapping  edges 
of  laminated  Conococheague  limestone  may  be  noted.  One- 
eighth  natural  size. 

Cambrian   (Ozarkian),  Conococheague  Is.,  one  mile  south  of 
Clear  Spring,  Maryland. 
Figures  1  to  8  are  after  Walcott. 


377 


MARYLAND  GEOLOGICAL  SURVEY 


CAMBRIAN  AND  ORDOVICIAN,  PLATE  XXVII 


UPPER  CAMBRIAN   (OZARKIAN).      CONOCOCHEAGUE  LIMESTONE  FOSSILS. 


PLATE  XXVIII 

PAGE 

Figs.  1,  2.     CBYPTOZOON  PBOLIFEKUM  Hall 189 

1.  Edge  view  of  a  fragment  showing  the  varying  diameter  of  the 

bodies  formed  by  the  undulating  layers  in  this  species.  At 
the  top  the  laminae  are  less  undulating  and  in  fact  become 
almost  horizontal.  This  upper  portion  represents  the  beginning 
of  a  new  growth  of  the  organism. 

2.  Photograph  of  a  fragment  illustrating  the  view  which  would  be 

seen  in  a  cross-section  taken  through  the  middle  line  of  Fig.  1. 
The  variable  diameter  of  the  concentric  masses  is  characteristic. 
Cambrian  (Ozarkian),  Conococheague.  Near  crossing  of  the 
Norfolk  and  Western  Railroad  and  turnpike,  one  mile  south- 
west of  Antietam  Station,  Maryland. 


378 


MARYLAND  GEOLOGICAL  SURVEY 


CAMBRIAN  AND  ORDOVICIAN,  PLATE  XXVIII 


UPPER  CAMBRIAN   (OZARKIAN).       CONOCOCHEAGUE  LIMESTONE  FOSSILS. 


PLATE  XXIX 

PAGE 

Fig.  1.    CBYPTOZOON  PBOLIFEBUM  Hall 189 

Photograph  of  the  upper  side  of  a  well  preserved  example  of  this 
characteristic  fossil,  the  original  of  which  is  22  inches  wide. 
The  unequal  size  of  the  confluent  heads  is  a  characteristic 
feature  in  this  species. 

Cambrian  (Ozarkian),  Hoyt  Is.  near  Saratoga  Springs,  New 
York. 

Fig.  2,  3.    CBYPTOZOON  UNDULATUM  Bassler  n.  sp 190 

2.  Edge  view  of  lower  portion  of  a  specimen  showing  the  rather  evenly 

undulating  layers  which  form  a  pseudocolumnar  structure. 

3.  Under  side  of  same  specimen  illustrating  the  relatively  equal  pro- 

portions of  the  areas  formed  by  the  undulating  layers. 

Cambrian  (Ozarkian),  Conococheague  Is.,  one  mile  south  of 
Pleasant  Hill  School  (2%  miles  southeast  of  Funkstown), 
Maryland. 


370 


MARYLAND  GEOLOGICAL  SURVEY 


CAMBRIAN  AND  ORDOVICIAN,  PLATE  XXIX 


'It 


2  3 

UPPER  CAMBRIAN    (OZARKIAN).      CONOCOCHEAGUE  LIMESTONE  FOSSILS. 


PLATE  XXX 

PAGE 

CBYPTOZOON  UNDULATUM  Bassler  n.  sp 190 

Edge  view  of  a  specimen,  two-thirds  natural  size.  In  the  lower  third 
the  laminae  are  undulated  strongly,  giving  the  appearance  of 
vertical  columns  in  cross-section.  The  undulation  is  less  pro- 
nounced in  the  middle  third  but  the  laminae  are  still  quite 
distinct.  In  the  upper  third  above  the  black  line  the  distinct 
lamination  disappears  and  the  layers  show  the  beginning  of  a 
new  growth  which  is  again  quite  undulating. 

Cambrian  (Ozarkian),  Conococheague  Is.,  one  mile  south  of 
Pleasant  Hill  School  (2%  miles  southeast  of  Funkstown), 
Maryland. 


380 


MARYLAND  GEOLOGICAL  SURVEY 

-••>?.*-    ^ 


CAMBRIAN  AND  ORDOVICIAN,  PLATE  XXX 


PLATE  XXXI 

PAGE 

Fig.  1.    PAL.EOPHYCUS  TUBULARE  Hall 192 

View  of  the  cylindrical  stems  of  this  species,  two-thirds  natural  size. 
Ordovician  (Canadian),  Tribes  Hill  Is.  of  New  York. 

Figs.  2-5.    OPHILETA  COMPLANATA  Vanuxem 302 

2, 3.  Top  and  side  views  of  the  type  of  Pleurotomaria  hunterensis 
Cleland,  representing  a  large  specimen  of  Ophileta  complanata. 
4,  5.  Lower  and  upper  views  of  a  smaller  specimen. 

Ordovician    (Canadian),  Tribes  Hill  Is.,  Fort  Hunter,  New 
York. 

Fig.  6.     PLEUBOTOMARIA  FLOBIDENSIS  Cleland 291 

Enlarged  view  of  the  type  example. 

Ordovician    (Canadian),  Tribes  Hill  Is.,  Fort  Hunter,  New 
York. 

Figs.  7-12.    DALMANELLA  WEMPLEI  Cleland 246 

7.  A  large  brachial  valve.     X  2. 

8,  9.  Two  pedicle  valves  with  side  outline  of  one.    X  2. 

Ordovician  (Canadian),  Kittatinny  Is.,  Columbia,  New  Jersey. 
10.  Brachial  valve. 

11, 12.  Two  pedicle  valves,  showing  alternation  of  coarse  and   fine 
costae. 

Ordovician    (Canadian),  Tribes  Hill  Is.,  Fort  Hunter,  New 
York. 

Figs.  13,  14.    RIBEIBIA  NUCULITIFOBMIS  Cleland 362 

13.  Lateral  view  of  well  preserved  cast  showing  the  notch. 

14.  Posterior  view  of  a  cast. 

Ordovician    (Canadian),  Tribes  Hill  Is.,  Fort  Hunter,  New 
York. 

Figs.  15-17.    RAPHISTOMA  ?  OBTUSUM  Cleland 307 

Upper,  side,  and  lower  views  of  the  type,  enlarged. 

Ordovician    (Canadian),  Tribes  Hill  Is.,  Fort  Hunter,  New 
York. 

Figs.  18,  19.     OPHILETA  LEVATA  Vanuxem 304 

Top  and  side  views  of  the  type  of  Ophileta  discus  Cleland  determined 
by  that  author  to  be  the  same  as  Ophileta  levata. 

Ordovician    (Canadian),  Tribes  Hill  Is.,  Fort  Hunter,  New 
York. 

Figs.  20,  21.    ECCLIOMPHALUS  MULTISEPTABIUS  Cleland 305 

20.  Top  view  of  the  type. 

21.  Natural  section  showing  the  partitions. 

Ordovician    (Canadian),  Tribes  Hill  Is.,  Fort  Hunter,  New 
York. 

Figs.  22,  23.    RAPHISTOMA  COLUMBIANUM  Weller 307 

Top  view  and  side  outline  of  the  type  example. 

Ordovician     (Canadian),    Kittantinny    Is.,    Columbia,    New 
Jersey. 

Fig.  1  after  Hall,  2-6,  10-21  after  Cleland,  and  7-9,  22-23  after 
Weller. 

381 


MARYLAND  GEOLOGICAL  SURVEY 


CAMBRIAN  AND  ORDOVICIAN,  PLATE  XXXI 


1 


FOSSILS  OF  BEEKMANTOWN  LIMESTONE   (STONEHENGE  MEMBER). 


PLATE  XXXII 

PAGE 

Figs.  1,  2.    CYBTOCERAS  BEEKMANENSE  Whitfield 330 

1.  Lateral  view  of  an  incomplete  shell,   showing  septa  and  living 

chambers. 

2.  Ventral  view  of  same  specimen. 

Ordovician  (Canadian),  Beekmantown  Is.  (Division  D.  1), 
Beekmantown,  N.  Y. 

Figs.  3,  4.    CYBTOCEBAS  GBACILE  Cleland 329 

Ventral  and  lateral  views  of  the  type. 

Ordovician  (Canadian),  Tribes  Hill  Is.,  Fort  Hunter,  New 
York. 

Fig.  5.    OBTHOCEBAS  PBIMIGENIUM  Vanuxem 322 

Natural  longitudinal  section,  illustrating  tapering  of  shell  and  close- 
ness of  septa. 

Ordovician  (Canadian),  Beekmantown  Is.,  Beekmantown, 
New  York. 

Figs.  6,   7.     CYCLOSTOMICEBAS  CASSINENSE    (Whitfield) 331 

Lateral  and  ventral  views  of  a  young  specimen  preserving  only  the 
living  chamber  and  several  septa. 

Ordovician  (Canadian),  Beekmantown  Is.,  Cassin  beds,  Fort 
Cassin,  Vermont. 

Figs.  8-10..    ASAPHELLUS  GYBACANTHUS  Raymond 345 

8.  Pygidium. 

9.  Free  cheek. 

10.  An  imperfect  cranidium. 

Ordovician  (Canadian),  Tribes  Hill  Is.,  Fort  Hunter,  New 
York. 

Figs.  11-15.    HEMIGYBASPIS  COLLIEANA  Raymond 346 

11.  An  imperfect  cranidium. 

12.  A  free  cheek.     X  2. 

13.  Well  preserved  pygidium. 

14.  An  imperfect  pygidium. 

15.  Hypostoma. 

Ordovician  (Canadian),  Stonehenge  Is.,  Bellefonte,  Pennsyl- 
vania. 

Figs.  16-18.    SYMPHYSUBUS  CONVEXUS  (Cleland) 347 

16.  The  cranidium  figured  by  Weller  as  Illaenurus  columMana. 

Ordovician  (Canadian),  Kittatinny  Is.,  Columbia,  New  Jersey. 

17.  18.    Two  small  pygidia. 

Ordovician,  Tribes  Hill  Is.,  Fort  Hunter,  New  York. 

Figs.  19,  20.    OOCEBAS  KIBBYI  (Whitfield) 328 

19.  Lateral  view  of  the  type. 

20.  View  of  the  outer  chamber  separated  from  the  shell  to  show  depth 

of  the  septum. 

Ordovician  (Canadian),  Beekmantown  Is.  (Division  D.  1), 
Beekmantown,  New  York. 

Figs.  1,  2,  5,  19,  20  are  after  Whitfield;  6,  7  after  Ruedemann; 
3,  4  after  Cleland;  and  8,  18  after  Raymond. 

382 


MARYLAND  GEOLOGICAL  SURVEY 


CAMBRIAN  AND  ORDOVICIAN,  PLATE  XXXII 


FOSSILS  OF  BEEKMANTOWN  LIMESTONE    (STONEHENGE  MEMBER), 


26 


PLATE  XXXIII 

PACK 

Figs.  1-3.    OPHILETA  COMPACTA  Salter 304 

I,  2.  Lower  and  upper  sides  of  a  specimen. 

3.  Schematic  cross-section  of  the  same. 

Ordovician  (Canadian),  Beekmantown  Is.,  Beekmantown, 
New  York. 

Figs.  4,  5.    SYNTKOPHIA  LATERALIS  Whitfield 267 

4.  Pedicle  valve.    X  2. 

5.  Sketch  of  hinge  of  same. 

Ordovician  (Canadian),  Kittatinny  Is.,  Columbia,  New 
Jersey. 

Figs.  6,  7.    ECCUOPTERUS  TRIANGULUS  (Whitfield) 302 

6.  7.  Top  and  side  views  of  a  cast  of  the  interior. 

Ordovician  (Canadian),  Beekmantown  Is.,  Providence  Island, 
Vermont. 

Figs.  8,  9.    MACLUKITES  AFFINIS  (Billings) 297 

8.  Top  view. 

9.  Cross-section  of  the  shell. 

Ordovician  (Canadian),  Division  F  of  Quebec  group.  Keppel 
Island,  Newfoundland. 

Figs.  10-12.    HYSTBICURUS  CONICUS  (Billings) 340 

10.  Glabella.     X  2. 

II.  Pygidium.     X  2. 

12    Profile  of  glabella  in  outline. 

Ordovician  (Canadian),  Beekmantown  Is.,  Beekmantown, 
New  York. 

Figs.  13-15.    TETRADIUM  SIMPLEX  Bassler  n.  sp 199 

13.  Weathered  fragment  of  limestone  showing  edge  view  of  tubes. 

14.  Top  view  of  corallum. 

15.  Portion  of  same.     X  4. 

Ordovician  (Canadian),  lower  part  of  the  Beekmantown  Is. 
just  above  the  Stonehenge  member,  eastern  edge  of  Hagerstown, 
Maryland. 

Figs.  1-3,  10-12  are  after  Whitfield;  4,  5,  after  Weller;  6,  7, 
after  Ulrich;  and  8  and  9  after  Billings. 


383 


MARYLAND  GEOLOGICAL  SURVEY 


CAMBRIAN  AND  ORDOVICIAN,   PLATE  XXXIII 


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14 


FOSSILS  OF  BEEKMANTOWN  LIMESTONE  (CRYPTOZOON  STEELI  ZONE). 


PLATE  XXXIV 

PAGE 

Fig.  1.    CBYPTOZOON  STEELI  Seely 191 

A  small  weathered,  rounded  specimen. 

Ordovician   (Canadian),  Cryptozoon  steeli  zone  of  the  Beek- 
mantown  Is.,  near  Williamsport,  Maryland. 

Fig.  2.    OPHILETA  COMPACTA  Salter 304 

Casts  of  two  examples  embedded  in  the  rock. 

Ordovician  (Canadian),  Cryptozoon  steeli  zone  of  the  Beek- 
mantown  Is.,  Paradise  Church,  Maryland. 

Fig.  3.    ECCYLIOMPHALUS  sp 305 

Specimen  of  a  small  narrow  species.  The  ridges  running  across  the 
shell  are  calcite-filled  fractures  of  the  rock. 

Ordovician    (Canadian),    Beekmantown    Is.,    near    Paradise 
Church,  Maryland. 

Fig.  4.    ECCYLIOMPHALUS  sp 305 

Sections  of  several  examples  of  an  undetermined,  large,  loosely- 
coiled  gastropod  shell. 

Ordovician  (Canadian),  Beekmantown  Is.,  lower  part,  Hagers- 
town,  Maryland. 

Fig.  5.    CYRTOCERAS  ?  sp 329 

View  of  a  curved  cephalopod  showing  appearance  on  a  weathered  sur- 
face. In  the  fresh  rock  all  trace  of  the  structure  is  generally 
gone. 

Ordovician    (Canadian),  Lower  Stonehenge  division  of  the 
Beekmantown  Is.,  near  Funkstown,  Maryland. 

Figures  3,  4  and  5  are  introduced  to  show  the  usual  aspect  of 
the  fossils  found  in  the  Beekmantown  limestone  of  Maryland. 


384 


MARYLAND  GEOLOGICAL  SURVEY 


CAMBRIAN  AND  ORDOVICIAN,  PLATE  XXXIV 


4  5 

FOSSILS  OF  BEEKMANTOWN  LIMESTONE  (CRYPTOZOON  STEELI  ZONE). 


PLATE  XXXV 

PAGE 

Figs.  1-3.     PLEUROTOMARIA  ??  GREG  ARIA  Billings 290 

1,  2.  Side  view  of  an  example  enlarged  and  natural  size. 
3.  Another  view  of  the  same. 

Ordovician  (Canadian),  Beekmantown  Is.,  St.  Ann,  Canada. 

Figs.  4,  5.    HORMOTOMA  GRACILENS  (Whitfleld) 293 

Two  nearly  complete  specimens.    Enlarged. 

Ordovician  (Canadian),  Beekmantown  Is.  (Division  D),  Beek- 
mantown, New  York. 

Fig.  6.     DALMANELLA  ELECTRA  (Billings) 245 

Pedicle  valve.    X  2. 

Ordovician  (Canadian),  Kittatinny  Is.,  Columbia,  New  Jersey. 

Figs.  7,  8.    MACLURITES  OCEANUS  (Billings) 299 

Top  and  side  views  of  the  type. 

Ordovician,  Quebec  group,  Port  aux  Choix,  Newfoundland. 

Figs.  9,  10.     ECCYLIOPTERUS  DISJUNCTUS  (Billings) 301 

9.  View  of  the  spire. 
10.  Lower  side  of  the  shell. 

Ordovician   (Canadian),  Beekmantown  Is.,  Leeds  and  Gren- 
ville  counties,  Canada. 

Fig.  11.    TURRITOMA  ACREA  (Billings) 293 

Drawing  of  the  type  specimen  natural  size. 

Ordovician    (Canadian),  Division  G  of  Quebec  group,  Port 
aux  Choix,  Newfoundland. 

Fig.  12.    ISOCHILINA  SEELYI  Whitfield 363 

View  of  a  right  valve  with  lateral  and  ventral  edge  views.    X  4. 

Ordovician  (Canadian),  Beekmantown  Is.,  Providence  Island, 
Lake  Champlain,  Vermont. 

Fig.  13.    CYRTOCERINA  MERCURIUS  Billings 331 

Side  view  of  the  type  specimen. 

Ordovician  (Canadian),  Point  Levis,  Quebec. 

Fig.  14.    TROCHOLITES  INTERNISTRIATUS  Whitfleld 326 

Lateral  view  of  specimen  showing  surface  sculpture  of  the  various 
stages  of  the  shell. 

Ordovician  (Canadian),  Beekmantown  Is.,  Cassin  beds,  Fort 
Cassin,  Vermont. 

.Fig.  15.    CAMEROCERAS  and  CYRTOCERINA 331 

A  group  of  specimens  showing  occurrence  and  condition  of  preserva- 
tion of  these  cephalopods  in  Maryland  strata.  The  two  left- 
hand  views  represent  a  species  of  Cyrtocerina.  The  remaining 
figures  are  of  an  undetermined  species  of  Cameroceras.  These 
fossils  occurred  as  imperfectly  silicifled,  iron-stained  pseudo- 
morphs  on  the  weathered  edges  of  rifts  and  caves  in  the  lime- 
stone. 

Ordovician  (Canadian),  Beekmantown  Is.,  quarries  at  Legore, 
Maryland. 

Figs.  1-3,  7-11,  and  13  are  after  Billings;   4,  5,  12  are  after 
Whitfield;  6  after  Weller;  and  14  after  Ruedemann. 

385 


MARYLAND  GEOLOGICAL  SURVEY 


CAMBRIAN  AND  ORDOVICIAN,  PLATE  XXXV 


FOSSILS  OF  THE  BEEKMANTOWN   LIMESTONE. 


PLATE  XXXVI 

PAGE 

Figs.  1-3.    MACLUEITES  SORDIDUS  (Hall) 298 

I,  2.     Lower  side  of  two  specimens. 

3.  Upper  side  of  a  partial  cast. 

Ordovician    (Canadian),    Beekmantown    Is.,    Beekmantown, 
New  York. 

Figs.  4,  5.    PLEUROTOMARIA  ??  CAXADENSIS  Billings 289 

4.  Side  view  of  a  cast. 

5.  View  showing  spire  of  specimen  with  shell  preserved. 

Ordovician   (Canadian),  Beekmantown  Is.,  Leeds  and  Gren- 
ville  counties,  Canada. 

Figs.  6,  7.    RAPHISTOMIXA  LAURENTIXA  (Billings) 308 

6.  Side  view. 

7.  Top  view  of  a  cast. 

Ordovician  (Canadian),  Romaine  formation,  Mingan  Islands, 
Canada. 

Figs.  8,  9.    HOBMOTOMA  ARTEMESIA  (Billings) 291 

8.  Cast  of  the  interior  of  a  fragment. 

9.  A  partly  restored,  well  preserved  specimen. 

Ordovician   (Canadian),  Beekmantown  Is.,  Leeds  and  Gren- 
ville  counties,  Canada. 

Figs.  10-12.    ISOCHILIXA  GREGARIA  Whitfield 363 

10.  View  of  right  valve  and  outline  showing  elevation.    X  4. 

II.  Left  valve  of  a  larger  example,  with  sketch  of  outline.     X  4. 
12.  Internal  cast  of  right  valve  and  outline.    X  4. 

Ordovician  (Canadian),  Beekmantown  Is.,  east  shore  of  Lake 
Champlain,  Vermont. 

Fig.  13.    PLIOMEROPS  SALTERI  (Billings) 359 

Pygidium.    Enlarged. 

Ordovician     (Canadian),     Beekmantown     Is.,     Phillipsburg, 
Quebec. 

Fig.  14.    GONIURUS  CAUDATUS  (Billings) 340 

Pygidium,  illustrating  the  large  triangular. spine. 

Ordovician    (Canadian),  Division  G  and  H   of  the   Quebec 
group.    Port  aux  Choix,  Newfoundland. 

Fig.  15.    CERATOPEA  KEITHI  Ulrich 299 

Side  and  edge  views  of  a  group  of  specimens. 

Ordovician     (Canadian),     Beekmantown,     Ceratopea     zone, 
western  edge  of  Bristol.     Tennessee  and  Wytheville,  Virginia. 
Figs.  1-3,  10-12  are  after  Whitfield;  4-9,  13,  and  14  are  after 
Billings. 

386 


MARYLAND  GEOLOGICAL  SURVEY 


CAMBRIAN  AND  ORDOVICIAN,  PLATE  XXXVI 


FOSSILS  OF  THE  BEEKMANTOWN   LIMESTONE. 


PLATE  XXXVII 

PAGE 
Figs.  1-4.    STROPHOMENA  STOSEI  Bassler  n.  sp 250 

1.  A  brachial  valve  and  interior  of  a  brachial  valve  nearby.     X  2.5. 

2.  A  pedicle  valve  of  a  specimen  referred  to  this  species  doubtfully  on 

account  of  its  high  hinge  area.    X  2.5. 

3.  A  crushed  pedicle  valve.    X  2.5. 

4.  Fragment  of  a  larger  shell  referred  to  the  species. 

Ordovician   (Chazyan),  Frederick  Is.,  stone  fences  just  east 
of  Frederick,  Maryland. 

Fig.  5.    RETEOCBINUS  ?  sp.  undet 209 

A  plate-like  structure  with  seven  rays.  X  6.  Other  examples  exhibit 
only  six  rays.  None  of  the  specimens  shows  a  basal  portion  con- 
necting the  rays. 

Ordovician  (Chazyan),  Frederick  Is.,  just  east  of  Frederick, 
Maryland. 

Figs.  6-8.    ACIDASPIS  ULBICHI  Bassler  n.  sp 355 

Three  specimens  illustrating  the  unusual  development  of  long  spines 
not  only  along  the  free  cheeks  but  even  to  the  tip  of  the  genal 
spine,  and  the  extraordinary  curvature  suggesting  that  the 
spines  were  directed  over  the  thorax.  X  2. 

Ordovician  (Chazyan),  Frederick  Is.,  east  of  Frederick,  Mary- 
land. 

Fig.  9.    ISOTELUS  sp.  undet 345 

Imperfect  free  cheek.    X  1.5. 

Ordovician  (Chazyan),  Frederick  Is.,  east  of  Frederick,  Mary- 
land. 

Fig.  10.    CAMEROCEKAS  sp 321 

Endosiphuncle  composed  of  crystalline  matter,  embedded  in  limestone. 
Ordovician  (Chazyan),  Frederick  Is.,  east  of  Frederick,  Mary- 
land. 


387 


MARYLAND  GEOLOGICAL  SURVEY 


CAMBRIAN  AND  ORDOVICIAN,  PLATE  XXXVII 


8  10 

FOSSILS  OF  THE  FREDERICK  LIMESTONE. 


PLATE  XXXVIII 

PAGE-, 

Figs.  1-5.    HEBEBTELLA  VULGABIS  Raymond 239' 

1-2.  Three  views  of  a  small  specimen  with  direct  striae.    X  1.5. 
4,  5.  A  large  specimen  exhibiting  some  bifurcating  striae.    X  2. 
Ordovician  (Chazyan),  Chazy,  New  York. 

Figs.  6-8.    DINOBTHIS  (PLAESIOMYS)  PLATYS  (Billings) 247' 

6.  Brachial  valve. 

7.  Edge  view  of  shell. 

8.  Pedicle  valve. 

Ordovician  (Chazyan),  Montreal,  Canada. 

Figs.  9-12.     HEBEBTELLA  BOBEALIS   (Billings) 238. 

9-11.  Three  views  of  a  specimen. 

12.  An  example  with  very  short  hinge  line. 

Ordovician  (Chazyan),  near  Montreal,  Canada. 

Figs.  13-15.    TETBADIUM  SYBINGOPOBOIDES  Ulrich 200 

13.  Surface  of  a  weathered  slab  showing  usual  aspect  of  the  species. 

14.  Portion  of  the  same  illustrating  tubes  in  more  detail.     X  3. 

15.  Drawing  of  a  transverse  section  illustrating  the  usual  appearance 

of  the  tubes  (at  the  top),  the  development  of  the  characteristic 
four  septa  (in  the  middle),  and  two  tubes  still  united  (at  bottom 
of  figure).  X  6. 

Ordovician  (Chazyan),  upper  part  Stones  Rives  Is.,  Pinesburg 
Station,  Maryland. 

Figs.  1-5,  9-12  are  after  Raymond  and  6-8  are  after  Billings. 


388 


MARYLAND  GEOLOGICAL  SURVEY 


CAMBRIAN  AND  ORDOVICIAN,  PLATE  XXXVIII 


13  14 

FOSSILS  OF  THE  STONES  RIVER  LIMESTONE. 


PLATE  XXXIX 

PAGE 

Figs.  1.5.    LOPHOSPIBA  BICINCTA  (Hall) 294 

1.  A  perfect,  silicified  shell. 

2.  Portion  of  the  last  whorl  of  same,  showing  direction  and  regularity 

of  lines  of  growth.     X  2. 

3.  Right  side  of  last  whorl  of  Fig.  1. 

Ordovician  (Chazyan),  Stones  River  Is.,  Murfreesboro,  Ten- 
nessee. 

4.  A  large  cast  of  the  interior  on  which  some  of  the  external  lines  of 

growth  are  obscurely  preserved. 

Ordovician  (Chazyan),  Black  River  group,  Beloit,  Wisconsin. 

5.  Vertical  section  of  an  elongated  specimen. 

Ordovician  (Chazyan),  Black  River  group,  Dixon,  Illinois. 

Figs.  6-8.    BUCANIA  SULCATINA  (Emmons) 309 

6.  Side  view  of  a  large  individual. 

7.  View  of  a  specimen.    X  2. 

8.  A  young  individual.     X  6. 

Ordovician  (Chazyan),  Lake  Champlain  area. 

Figs.  9-11.    AMPYX  (LONCHODOMAS)  HALLI  (Billings) 337 

9.  Head  with  rostral  spine  broken. 

10.  Pygidium  with  two  of  thoracic  segments. 

11.  Side  view  of  head. 

Ordovician  (Chazyan),  Highgate  Springs,  Vermont. 

Figs.  12-15.    MACLUBITES  MAGNUS  Lesueur 297 

12-14.  Top,   side,   and   botttom   views  of   same   specimen,   two-thirds 

natural  size. 

15.  Interior  view  of  an  operculum,  two-thirds  natural  size. 
Ordovician  (Chazyan),  Lake  Champlain  area. 

Fig.  16.    LEPERDICIA  FABULITES  Conrad  var 364 

Surface  of  slab  with  numerous  examples  of  this  variety.     X  1.3. 

Ordovician    (Chazyan),    Stones   River    group,    Lebanon    Is., 
Columbia,  Tennessee. 

Figs.  1-5  are  after  Ulrich  and  Scofield;   6-8,  12-14  are  after 
Raymond;  and  9-11  are  after  Billings. 


389 


MARYLAND  GEOLOGICAL  SURVEY 


CAMBRIAN  AND  ORDOVICIAN,  PLATE  XXXIX 


16 
FOSSILS  OF  THE  STONES  RIVER  LIMESTONE. 


PLATE  XL 

PAGE 

Figs.  1-3.    HELOPORA  DIVARICATA  Ulrich 227 

1.  Segment  natural  size  and  X  7. 

2.  Portion  of  the  same.    X  18. 

3.  Transverse  section.    X  18. 

Ordovician    (Mohawkian),    Black   River    (Decorah)    shales, 
Minneapolis,  Minnesota. 

Figs.  4-6.    CHASMATOPORA  RETICULATA  (Hall) 226 

4.  Frond  showing  the  reverse  side. 

5.  Portion  of  the  same.    X  9. 

6.  Small  fragment  exhibiting  the  reverse  or  celluliferous  side.     X  18. 

Ordovician     (Mohawkian),     Trenton     shales,     Minneapolis, 
Minnesota. 

Figs.  7-10.    CHASMATOPORA  SUBLAXA  (Ulrich) 227 

7.  8.  Fragments  showing  obverse  and  reverse  sides. 

9.  Celluliferous  side  of  specimen,  Fig.  7.    X  9. 

10.  Reverse  side  of  small  fragment,  Fig.  8,  illustrating  striated  char- 

acter.   X  9. 

Ordovician    (Mohawkian),    Black   River    (Decorah)    shales, 
Minneapolis,  Minnesota. 

Figs.  11-14.    ESCHAROPORA  CONFLUENS  Ulrich 223 

11.  A  specimen  preserving  the  pointed  articulating  base. 

12.  Surface  of  example  illustrating  arrangement  of  apertures.     X  9. 

13.  Vertical  section.     X  18. 

14.  Tangential  section  of  a  well  preserved  fragment.     X  18. 

Ordovician    (Mohawkian),   Black   River    (Decorah)    shales, 
Minneapolis,  Minnesota. 
Figures  after  Ulrich. 


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27 


PLATE  XLI 

PAGE 

Figs.  1-3.    SOLENOPOBA  coMPACTA  Billings 192 

1.  View  of  a  small  mass. 

2,  3.  Longitudinal  and  transverse  sections.     X  35. 

Ordovician  (Mohawkian),  Black  River  (Decorah)  shales,  near 
Cannon  Falls,  Minnesota. 

Fig.  4.    TETRADIUM  COLUMNABE  (Hall) 201 

Fragment  of  a  corallum. 

Ordovician    (Mohawkian),  Trenton  Is.,  Lewis  County,  New 
York. 

Fig.  5.    COLUMNARIA  HALLi  Nicholson 198 

Corallum  showing  the  little  extension  of  the  septa  in  the  tubes. 
Ordovician  (Mohawkian),  Trenton  Is.  of  Canada. 

Fig.  6.    HEBERTELLA  BELLARUGOSA  (Conrad) 239 

Exterior  of  a  brachial  valve. 

Ordovician  (Mohawkian),  Trenton  shales  of  Minnesota. 

Fig.  7.    CABYOCYSTITES  sp 208 

A  weathered  plate  of  this  cystid  showing  the  pores.    X  4. 

Ordovician,  Caryocystites  bed  of  the  Chambersburg  Is.,  Fort 
London,  Pennsylvania. 

Figs.  8,  9.    RAFINESQUINA  CHAMPLAINENSIS  Raymond 261 

8.  Specimen  exhibiting  brachial  valve,  cardinal  area,  and  deltidium. 

9.  Pedicle  valve. 

Ordovician  (Chazyan),  New  York. 

Fig.  10.    CARABOCBINXJS  sp 209 

An  imperfect  plate. 

Ordovician,    Caryocystites    bed    of    Chambersburg   Is.,    Fort 
London,  Pennsylvania. 

Figs.  11-13.    LEPTAENA  CHABLOTTAE  Winchell  and  Schuchert 257 

Views  of  the  pedicle  and  brachial  valve  and  side  outline  of  the  same 
specimen. 

Ordovician    (Mohawkian),    Black   River    (Decorah)    shales, 
St.  Paul,  Minnesota. 

Figs.  14-16.    CAMABOTOECHIA  PLENA  (Hall) 270 

Views  of  the  pedicle  and  brachial  valves  and  side  outline  of  an  average 
specimen. 
Ordovician  (Chazyan),  Canada. 

Fig.  17.    HEBEBTELLA  BOBEALIS  (Billings) 238 

An  example  showing  the  pedicle  valve. 

Ordovician  (Chazyan),  near  Montreal,  Canada. 

Fig.  18.    HEBEBTELLA  VULGABIS  Raymond 239 

Pedicle  valve  of  a  large  example.     X  2. 

Ordovician  (Chazyan),  New  York. 

Fig.  19.    GONIOCEBAS  CHAZIENSE  Ruedemann 328 

An  imperfect  specimen  showing  the  arrangement  of  the  septa. 

Ordovician,  Carocystites  bed  of  the  Chambersburg  Is.,  Fort 
Loudon,  Pennsylvania. 

Figs.  1-3,  6,  11-13,  are  after  Winchell  and  Schuchert;  4  after 
Hall;  5,  14-16,  after  Billings;  and  8,  9,  17, 18,  after  Raymond. 

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MARYLAND  GEOLOGICAL  SURVEY 


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18 
FOSSILS  OF  THE  CHAMBERSBURG  LIMESTONE   ( CARYOCYSTITES  BED). 


PLATE  XLII 

PAGE 

Figs.  1,  2.    STREPTELASMA  PBOFUNDUM  (Conrad) 199 

1.  An  entire  specimen  with  a  portion  broken  away  to  show  the  great 

depth  of  the  body  cavity. 

2.  View  of  the  body  cavity. 

Ordovician  (Mohawkian),  Black  River  (Platteville)  Is., 
Mineral  Point,  Wisconsin. 

Figs.  3-5.    TETRADIUM  CELLULOSUM  (Hall) 202 

3.  Section  in  the  rock  cutting  the  tubes  longitudinally  and  showing 

their  arrangement  in  bundles. 

4.  Portion  of  two  bundles,  enlarged. 

5.  Cross-section  in  rock,  exhibiting  the  arrangement  of  the  tubes  and 

the  occurrence  of  the  characteristic  four  septa. 

Ordovician  (Mohawkian),  Black  River  Is.,  Watertown,  N.  Y. 

Fig.  6.    CAMAROCLADIA  BUGOSA  Ulrich 196 

Rock  fragment  composed   almost  entirely  of  the  branches   of  this 
organism. 

Ordovician  (Mohawkian),  Black  River  (Decorah)  shales, 
St.  Paul,  Minnesota. 

Figs.  7,  8.    ORBIGNYELLA  WETHERBYI  (Ulrich) 214 

7.  Vertical  section  exhibiting  the  characteristic  curved  diaphragms. 

X  18. 

8.  Tangential  section  showing  the  angular  tubes  and  the  granular 

walls.     X  18. 

Ordovician  (Mohawkian),  Black  River  (Platteville)  Is., 
Minneapolis,  Minnesota. 

Figs.  9-12.    ZYGOSPIRA  RECUBVIBOSTRIS  (Hall) 272 

9.  10.  Brachial  and  pedicle  valves  of  an  entire  specimen.     X  2. 
11,  12.  Anterior  and  lateral  views  of  the  same. 

Ordovician  (Mohawkian),  Trenton  portion  of  the  Jackson- 
burg,  Is.,  Jacksonburg,  New  Jersey. 

Figs.  13-15.    HELICOTOMA  PLANULATOIDES  Ulrich 300 

Three  views  of  an  entire  silicified  specimen. 

Ordovician  (Mohawkian),  Black  River  (Lowville)   Is.,  Mercer 
County,  Kentucky. 

Figs.  16,  17.    HELICOTOMA  VERTICALIS  Ulrich 301 

Basal  and  lateral  views  of  a  cast  of  the  interior. 

Ordovician  (Mohawkian),  Black  River  (Lowville)  Is.,  High 
Bridge,  Kentucky. 

Figs.  18-20.    CTENODONTA  GIBBEBULA  Salter 277 

18.  Lateral  view  of  a  large  right  valve. 

19.  Cardinal  view  of  the  same. 

Ordovician  (Mohawkian),  Stones  River  (Murfreesboro)  Is., 
Murfreesboro,  Tennessee. 

Fig.  1,  2  are  after  Winchell  and  Schuchert;  3-5  are  after  Hall; 
7,  8,  18-20  are  after  Ulrich;  9-12  are  after  Weller;  and  13-17  are 
after  Ulrich  and  Scofield. 


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PLATE  XLIII 

PAGE 

Figs.  1-5.    LEPEBDITIA  FABULITES  (Conrad) 364 

1.  Cast  of  interior  of  right   (larger)   valve  showing  impressions  of 

papillae  along  ventral  margin.     X  2. 

2,  3.  Ventral  and  dorsal  views  of  a  complete  carapace.     X  2. 

4.  Left  valve  of  the  same.     X  2. 

5.  Posterior  view.     X  2. 

Ordovician  (Mohawkian),  Black  River  (Platteville)  Is., 
Minneapolis,  Minnesota. 

Figs.   6-9.     MACBONOTEULA  ULBICHI  Ruedemann 368 

6.  7.  Ventral  and  lateral  views  of  a  large  valve.     X  14. 

8, 9.  Similar  views  of  another  specimen  showing  the  specific  char- 
acters well  developed.     X  14. 

Ordovician  (Mohawkian),  Rysedorph  conglomerate,  Ryse- 
dorph  Hill,  Rensselaer  County,  New  York. 

Figs.  10-12.    LEPEBDITELLA  TUMIDA  (Ulrich) 366 

10.  Right  valve.     X  10. 

11, 12.  Dorsal  and  posterior  views  of  same  in  outline.     X  10. 

Ordovician  (Mohawkian),  Black  River  (Lowville)  Is.,  High 
Bridge,  Kentucky. 

Figs.  13-15.    DREPANELLA  MACBA  Ulrich 367 

13.  Left  valve.    X  20. 

14, 15.  Sectional  views  of  same  between  points  marked  c  and  b. 

Ordovician  (Mohawkian),  Stones  River  (Lebanon)  Is.,  La- 
vergne,  Tennessee. 

Figs.  16,  17.    OMOSPIBA  ALEXANDRA  (Billings) 308 

16.  Cast  of  the  interior. 

Ordovician  (Mohawkian),  Black  River  (Platteville)  Is., 
Dixon,  Illinois. 

17.  An  imperfect,  silicified  shell. 

Black  River  (Lowville)  Is.,  Mercer  County,  Kentucky. 

Figs.  18-21.    PTEBYGOMETBOPUS  CALLICEPHAI.US  (Hall) 360 

18.  A  nearly  complete  pygidium  of  large  size. 

19.  A  small  complete  pygidium. 

20.  An  incomplete  head. 

Ordovician  (Mohawkian),  Trenton  portion  Jacksonburg  Is., 
Jacksonburg,  New  Jersey. 

21.  Complete  individual. 

Ordovician  (Mohawkian),  Trenton  Is.  of  Canada. 

Figs.  22,  23.    CERAUBUS  PLEUREXANTHEMUS  Green 358 

22.  An  incomplete  cranidium. 

Ordovician  (Mohawkian),  Trenton  portion  of  Jacksonburg  Is., 
Jacksonburg,  New  Jersey. 

23.  General  aspect  of  species  of  this  type.    The  original  of  this  figure 

has  since  been  referred  to  a  new  species,  C.  dentatus  Raymond 
and  Barton. 

Trenton. Is.,  of  Canada. 

Figs.  1-5,  10-15  are  after  Ulrich ;  6-9  after  Ruedemann ;  16,  17, 
21,  23  after  Billings;  18-20,  22  after  Weller. 

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PLATE  XLIV 

PAGE 

Figs.  1-5.    HEMIPHBAGMA  IBRASUM  (Ulrich) 218 

1.  Surface  of  a  zoarium  illustrating  the  usual  aspect.    X  10. 

2.  Tangential  section.    X  18. 

3.  Vertical  section  exhibiting  incomplete  diaphragms  in  mature  zone. 

X9. 

4.  5.  Two  specimens  of  the  branching  zoarium. 

Ordovician   (Mohawkian),  Black  River  (Decorah)   shales  of 
Minnesota. 

Figs.  6,  7.    DIANULTTES  PETROPOLITANUS  Dybowski 217 

6.  Vertical  section.     X  9. 

7.  Tangential  section  X  9  and  a  portion  X  35  showing  wall  structure 

in  detail. 

Ordovician   (Mohawkian),  Trenton  shales,  Goodhue  County, 
Minnesota. 

Figs.  8-10.    HELOPORA  SPINIFORMIS  Ulrich 228 

8.  A  segment  natural  size  and  lower  portion  of  same.    X  18. 
9, 10.  Vertical  and  transverse  sections  of  a  segment.    X  18. 

Ordovician   (Mohawkian),  Stones  River   (Lebanon)    Is.,  La- 
vergne,  Tennessee. 

Figs.  11-14.    RHINIDICTYA  NEGLECTA  Ulrich 229 

11.  Fragment,  natural  size,  and  portion  of  surface  X  18,  showing  the 

usual  aspects  of  the  species. 

12.  Tangential  section.     X  18. 

13, 14.  Vertical  and  transverse  section.     X  18. 

Ordovician  (Mohawkian),  Trenton  Is.,  Burgin,  Kentucky. 

Figs.  15-17.    PRASOPORA  INBULARIS  Ulrich 215 

15.  Tangential  section  exhibiting  the  numerous  mesopores.     X  18. 

16.  Small  portion  of  a  tangential  section  through  a  macula  and  sur- 

rounding zooecia.    X  18. 

17.  Vertical  section  illustrating  great  abundance  of  cystiphragms  and 

diaphragms.    X  18. 

Ordovician  (Mohawkian),  Trenton  shales  near  Cannon  Falls, 
Minnesota. 

Figures  are  after  Ulrich. 


394 


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CAMBRIAN  AND  ORDOVICIAN,  PLATE  XtlV 


MiKM&K+T* 

iwEiiwr  *** 


15  17  16 

FOSSILS  OF  THE  CHAMBERSBURG  LIMESTONE   (ECHINOSPHERITES  BED) . 


PLATE  XLV 

PAGE 

Figs.  1-3.    PIANODEMA  suBEQUATA  (Conrad) 249 

Pedicle  and  brachial  valves  of  a  well  preserved  example  and  profile  of 
the  same. 

Ordovician  (Mohawkian),  Black  River  (Decorah)  shales, 
Minneapolis,  Minnesota. 

Fig.  4.    RAFINESQUINA  MINNESOTENSIS  (Winchell) 261 

Brachial  valve  of  the  type  form  of  this  species. 

Ordovician  (Mohawkian),  Black  River  Is.,  Rocktown,  Wis- 
consin. 

Figs.  5,  6.    RAFINESQUINA  MINNESOTENSIS  INQUASSA  (Sardeson) 264 

Dorsal  and  profile  views  of  an  ordinary  example  of  this  variety. 
Ordovician  (Mohawkian),  Black  River  (Platteville)  Is.,  Mineral  Point, 
Wisconsin. 

Fig.  7.    RECEPTACULITES  OCCIDENTALIS  Salter 194 

Weathered  surface  of  an  imperfect  specimen. 

Ordovician  (Mohawkian),  Black  River  portion  of  Jackson- 
burg  Is.,  near  Springdale,  New  Jersey. 

Figs.  8,  9.    DINOBTHIS  PECTINELLA  (Emmons) 248 

8.  Pedicle  valve. 

9.  Incomplete  brachial  valve. 

Ordovician  (Mohawkian),  Lowest  Trenton  portion  of  Jackson- 
burg  Is.,  near  Newton,  New  Jersey. 

Figs.  10-12.    HEBEBTELLA  BELLAKUGOSA  (Conrad) 239 

10.  Exterior  of  a  large  pedicle  valve. 

11.  Interior  of  the  same. 

12.  Exterior  of  a  dorsal  valve  of  the  ordinary  size. 

Ordovician  (Mohawkian),  Trenton  shales  of  Minnesota. 

Figs.  13,  14.    AMPYX  ( LONCHODOM AS )  NORMALIS  (Billings) 336 

Head  and  pygidium. 

Ordovician,  Chazyan  of  Newfoundland. 

Figs.  15-20.    ECHINOSPHERITES  AURANTIUM  var  AMERICANUM  Bassler  n.  var.  207 

15.  A  specimen  of  average  size  showing  the  ovate  form  of  this  variety. 

16.  A  well  preserved  small  example  preserving  the  point  of  attach- 

ment at  the  base.     X  2. 

17.  A  slightly  distorted  but  otherwise  typical  specimen. 

18.  Compressed  example  with  plates  exposed  by  weathering. 

19.  Abraded  outer  surface  of  the  plates  showing  pore  rhombs.    X  3. 

20.  Inner  surface  of  calyx  plates  exhibiting  pores.     X  3. 

Ordovician  (Mohawkian),  Echinospherites  bed  of  Chambers- 
burg  Is.,  3%  miles  north  of  Greencastle,  Pennsylvania. 

Figs.  1-3,  5,  6,  10-12  are  after  Winchell  and  Schuchert;  7-9 
after  Weller;  and  13,  14  after  Billings. 


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FOSSILS  OF  THE  CHAMBERSBURG  LIMESTONE   (ECHINOSPHERITES  BED). 


PLATE  XLVI 

PAGE 

Figs.  1-5.    NIDULITES  PYRIFOBMIS  Bassler 193 

1.  A  nearly  complete  example  partially  embedded  in  limestone.    The 

pyriform  shape  of  the  organism  is  shown. 

2.  Surface  of  same  showing  the  usual  aspect  of  the  cups.    X  4. 

3.  A  group  of  examples  on  a  limestone  slab  with  their  interior  filled 

with  crystalline  calcite. 

4.  A  fractured  piece  of  limestone  with  cross-sections  of  this  organism. 

5.  Weathered  rock  surface  with  Nidulites  in  various  positions. 

Ordovician  (Mohawkian),  Nidulites  bed  of  Chambersburg  Is., 
Strasburg,  Virginia. 


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CHAMBERSBURG  LIMESTONE   (NIDULITES  BED). 


PLATE  XLVII 

PAGE 

Figs.  1-3.    SCENIDIUM  ANTHONENSE  Sardeson 268 

1.  A  complete  brachial  valve.     X  2. 

2.  Incomplete  pedicle  valve.     X  2. 

3.  Profile  of  same.     X  2. 

Ordovician  (Mohawkian),  Black  River  portion  of  the  Jackson- 
burg  Is.,  Jacksonburg,  New  Jersey. 

Figs.  4-6.    ORTHIS  TBICENABIA  Conrad 240 

Brachial  and  pedicle  valves  of  a  complete  example  and  profile  view  of 
same. 

Ordovician    (Mohawkian),   Black   River    (Decorah)    shales, 
Minneapolis,  Minnesota. 

Figs.  7,  8.    PRASOPORA  CONTIGUA  Ulrich 216 

7.  Tangential  section  of  the  hemispheric  zoarium,  showing  the  com- 

parative fewness  of  mesopores.    X  16. 

8.  Vertical  section  illustrating  the  occurrence  of  cystiphragms  and 

also  the  small  number  of  mesopores.     X  18. 

Ordovician    (Mohawkian),   Black   River    (Decorah)    shales, 
Goodhue  County,  Minnesota. 

Figs.  9-11.    DIPLOTRYPA  ?  APPALACHIA  Bassler  n.  sp 219 

9.  View  of  the  hemispheric  zoarium,  basal  side  up  in  the  rock. 

10.  Tangential  section.     X  10. 

11.  Vertical  section.    X  10. 

Ordovician  (Mohawkian),  Nidulites  bed  of  Chambersburg  Is., 
Strasburg,  Virginia. 

Figs.  12-14.    CORYNOTRYPA  DELicATULA  ( James) 213 

12.  Zoarium  illustrating  the  elongate  club-shaped,  incrusting  zocecia. 

X  9. 

13.  Several  zocecia  of  the  same  zoarium  more  slender  than  usual.   X  25. 

14.  Unusually  large  zocecia  of  another  form  of  the  species.     X  25. 

Ordovician    (Mohawkian),   Black   River    (Decorah)    shales, 
St.  Paul,  Minnesota. 

Figs.  15-17.    CORYNOTRYPA  INFLATA  (Hall) 212 

15.  Small  portion  of  a  large  zoarium  growing  upon  a  brachiopod.   X  9. 

16.  Three  zocecia  of  one  form  of  the  species.     X  18. 

17.  Profile  view  of  a  zocecium. 

Ordovician    (Mohawkian),    Black   River    (Decorah)    shales, 
Cannon  Falls,  Minnesota. 

Fig.  18.    ONCHOMETOPUS  SIMPLEX  Raymond  and  Narraway 348 

An  imperfect  specimen  referred  to  the  species  on  account  of  its  general 
form  but  particularly  on  account  of  the  absence  of  a  concave 
border. 

Ordovician  (Mohawkian),  Nidulites  bed  of  Chambersburg  Is., 
Wilson,  Maryland. 

Figs.    1-3    are    after    Weller;    4-6    are    after    Winchell    and 
Schuchert;  7,  8,  12-17  after  Ulrich. 

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18 
FOSSILS  OF  THE  CHAMBERSBURG  LIMESTONE   (NIDULITES  BED). 


PLATE  XLVIII 

1'AGE 

Figs.  1-7.    PLECTAMBONITES  PISUM  Ruedemann 253 

1.  A  pedicle  valve  less  tumid  than  usual.     X  1.25. 

2.  Posterior  view  of  same.    X  1.25. 

3.  Pedicle  valve  of  normal  dimensions.     X  1.25. 

4.  Brachial  valve  of  an  entire  shell.     X  1.25. 

5.  Internal  cast  of  pedicle  valve  showing  casts  of  muscular  and  vas- 

cular impressions.     X  1.25. 

6.  Interior  view  of  brachial  valve.     X  1.25. 

7.  Pedicle  valve  with  long  cardinal  line.    X  1.25. 

Ordovician  (Mohawkian),  Rysedorph  conglomerate,  Ryse- 
dorph  Hill,  Rensselaer  County,  New  York. 

Figs.  8-11.    PARASTROPHIA  HEMIPLICATA  Hall 269 

8.  9.  Brachial  and  pedicle  views  of  an  entire  specimen. 
10, 11.  Anterior  and  lateral  views  of  the  same. 

Ordovician  (Mohawkian),  Lower  Trenton  portion  of  the  Jack- 
sonburg  Is.,  near  Newton,  New  Jersey. 

Fig.  12.    ORBICULOIDEA  LAMELLOSA  (Hall) 234 

Exterior  of  a  brachial  valve.     X  2. 

Ordovician  (Mohawkian),  Trenton  Is.,  Middleville,  New  York. 

Figs.  13-15.    ARTHROPOBA  BIFURCATA  Ulrica 224 

13.  Segment  natural  size. 

14.  Surface  of  upper  part  of  original  of  Fig.  15  showing  aged  condition 

of  zocecia.    X  18. 

15.  A  small  segment  natural  size  and  its  upper  part  X  18  illustrating 

the  youthful  condition. 

Ordovician  (Mohawkian),  Black  River  (Decorah)  shales, 
St.  Paul,  Minnesota. 

Figs.  16-18.     CHRISTIANIA  TRENTONENSIS  Ruedemann 256 

16.  Somewhat  exfoliated  pedicle  valve.    X  2. 

17.  Brachial  valve.    X  2. 

18.  Interior  of  brachial  valve  showing  the  quadrupal  adductor  scar 

divided  by  high  vertical  muscular  walls.     X  2. 

Ordovician  (Mohawkian),  Rysedorph  conglomerate,  Ryse- 
dorph Hill,  Rensselaer  County,  New  York. 

Figs.  19,  20.    ZYGOSPIRA  EXIGUA  (Hall) 273 

Pedicle  and  brachial  valves  illustrating  the  smooth  exterior.     X  2. 
Ordovician  (Mohawkian),  Trenton  Is.,  Watertown,  New  York. 

Fig.  21.    CYRTOCERAS  CAMURUM  Hall 330 

Type  specimen  showing  the  rapidly  curving  shell. 

Ordovician  (Mohawkian),  Trenton  Is.,  Middleville,  New  York. 

Fig.  22.    ORTHOCEHAS  ARCUOLIRATUM  Hall 323 

Fragment  of  the  shell,  exhibiting  the  arched  annulations. 

Ordovician  (Mohawkian),  Trenton  Is.,  Watertown,  New  York. 

Figs.  23-25.     ISOTELUS   GIGAS    DeKay 344 

23.  A  small  but  rather  perfect  specimen  of  the  spinous  form. 

24.  A  larger  example  of  same. 

25.  Aspinose  form. 

Ordovician  (Mohawkian),  Trenton  Is.,  near  Trenton  Falls, 
New  York. 

Figs.  1-7,  16-18  are  after  Ruedemann;  8-11,  13-15  are  after 
Ulrich;  12, 19,  20  are  after  Hall  and  Clarke;  21,  22  are  after  Hall. 

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28 


PLATE  XLIX 

PAGE 

Fig.  1.    STROPHOMENA  SCULPTURATA  Bassler  n.  sp 250 

Exterior  of  a  brachial  valve  illustrating  the  highly  ornamented  sur- 
face.   X  2. 

Ordovician  (Mohawkian),  Sinuites  bed  at  base  of  Martinsburg 
shale,  1  mile  south  of  St.  Thomas,  Pennsylvania. 

Fig.  2.    LEPTAENA  TENUISTRIATA  Sowerby  var 260 

Pedicle  valve  of  an  incomplete  specimen.     X  2. 

Ordovician   (Mohawkian),  Sinuites  bed  at  base  of  Martins- 
burg  shale,  1  mile  south  of  St.  Thomas,  Pennsylvania. 

Figs.  3-10.    CHRISTIANIA  LAMELLOSA  Bassler  n.  sp 257 

3, 4.  Pedicle   valve   showing  the   characteristic   lamellose   markings. 

Natural  size  and  X  2. 

5,  6.  Another  example  showing  pedicle  valve,  natural  size  and  X  2. 
7,  8.  Brachial  valve  of  another  specimen  natural  size  and  X  2. 
9, 10.  Interior  of  a  brachial  valve  illustrating  characteristic  muscular 
scars.    Natural  size  and  X  2. 

Ordovician  (Mohawkian),  base  of  Martinsburg  shale,  Stras- 
burg,  Virginia. 

Figs.  11-13.    TRIPLECIA  (CLIFTONIA)  SIMULATRIX  Bassler  n.  sp 266 

11.  Pedicle  valve  of  an  exfoliated  specimen. 

Ordovician   (Mohawkian),  Sinuites  bed  at  base  of  Martins- 
burg shale,  1  mile  south  of  St.  Thomas,  Pennsylvania. 
12, 13.  Brachial  valve  with  the  shell  preserved.     Natural  size  and 
enlarged. 

Ordovician   (Mohawkian),  base  of  Martinsburg  shale,  Stras- 
burg,  Virginia. 

Figs.  14-16.     LEPTOBOLUS  ?  OVALIS  Bassler  n.  sp 230 

14.  Exterior  of  pedicle  valve.    X  4. 

15.  Interior  of  brachial  valve  showing  the  median  and  lateral  septa. 

X4. 

16.  Interior  of  another  brachial  valve  with  markings  more  obscure. 

X4. 

Ordovician  (Mohawkian),  Sinuites  bed  at  base  of  Martinsburg 
shale,  2  miles  northwest  of  Kauffman,  Pennsylvania. 

Figs.  17-21.    DALMANELLA  EDSONI  Bassler  n.  sp 243 

17.  Interior  of  brachial  valve. 

18.  Pedicle  valve  of  incomplete  specimen  illustrating  the  strongly 

marked  ridges. 

19.  Brachial  valve  of  specimen  almost  complete. 

Sinuites  bed  at  base  of  Martinsburg  shale  1  mile  south  of 
St.  Thomas,  Pennsylvania. 

20.  Brachial  valve  of  partially  exfoliated  example. 

21.  Exfoliated  and  incomplete  pedicle  valve. 

Ordovician  (Mohawkian),  Trenton  limestone,  Shipyard  Bay, 
Highgate  Springs,  Vermont. 

Figs.  22,  23.    COLEOLUS  IOWENSIS  James 320 

22.  Rock  fragment  with  numerous  specimens  illustrating  the  long, 

slender  curved  form.    X  2. 

23.  Portion  of  the  same  showing  exterior  of  shells.    X  6. 

Richmond  group,  Maquoketa  shale,  Graf,  Iowa. 

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PLATE  L 

PAGB 

Figs.   1-5.     CONOTRETA  HDSTi  (Walcott) 234 

1.  Internal   cast  of   pedicle   valve   showing   impressions   of   the   strong   apical 

callosity  and  the  radiating  ridges.      X  8. 

2.  Apical  view  of  the  same.     The  subtriangular  posterior  slope  and  its  obscurely 

defined  median  furrow  are  visible.      X  9. 

3.  Cardinal  view  of  a  young  individual  with  very  faint  posterior  slope.      X  12. 

Ordqvician  (Mohawkian).     Trenton  Is.,  Trenton  Falls,  New  York. 

4.  Cardinal  view  of  very  small  example  retaining  the  shell.      X  25. 

5.  Profile   of   the    same. 

Ordovician   (Mohawkian)  Trenton  Is.,  Covington,  Kentucky. 

Figs.  6-8.     LINGULA  BICINIFORMIS  (Hall) 232 

6.  Well  preserved  ventral  valve. 

7.  Enlarged  sketch  of  the  posterior  portion  of  the  same  specimen  showing  growth 

stages,  p,  protegulum  ;  o,  obolella  ;  s,  nealogic. 

Ordovician   (Mohawkian)   Trenton  shale,  St.  Paul,  Minnesota. 

8.  A  nearly  complete,  partially  exfoliated  valve.      X  2. 

Ordovician  (Mohawkian)  Trenton  portion  of  Jacksonburg  Is.,  Jackson- 
burg,  New  Jersey. 

Figs.  9,  10.     DALMANELLA  TESTUDINARIA  (Dalman)  var 242 

9.  A  pedicle  valve.      X  2. 

10.  Brachial  valve.      X  2. 

Ordovician  (Mohawkian)  Trenton  portion  of  Jacksonburg  Is.,  Jackson- 
burg,  New  Jersey. 

Figs.   11-13.     HINDIA  PARVA  (Ulrich)    197 

11.  Three  specimens  showing  variations  in  size. 

12.  Vertical  section.     X  10. 

13.  Longitudinal  section.      X  10. 

Ordovician  (Mohawkian)  Trenton  shales,  Fillmore  County,  Minnesota. 

Figs.   14-16.     SCENIDIDM    ?  MEROPE    (Billings)    268 

Ventral  side,  area,  and  lateral  views  of  the  type. 

Ordovician  (Mohawkian)  Trenton  Is.,  Ottawa,  Ontario. 
Figs.  17-18.     CYRTOLITINA  NITIDULA  (Ulrich)   311 

Two  views  of  the  type.  The  specimen,  although  a  cast  of  the  interior, 
preserves  the  surface  markings.  X  2. 

Ordovician    (Mohawkian)    Trenton   Is.,   Covington,   Kentucky. 
Figs.  19,  20.     ECCYLIOMPHALUS  TRENTONENSIS    (Conrad)    306 

Two  views  of  an  incomplete  specimen. 

Ordovician    (Mohawkian)    Trenton    portion    of    the    Jacksonburg    Is., 
Jacksonburg,  New  Jersey. 
Figs.  21,  22.     MICROCERAS  INORNATUM  (Hall)    312 

Side  and  edge  views  of  a  complete  shell.     X  6. 

Ordovician   (Cincinnatian)   Maysville  group,  Cincinnati,  Ohio. 
Figs.  23-26.     CYCLORA  MINUTA   (Hall)    316 

23.  View  of  side  and  aperture.      X  6. 

24.  Under  side  of  shell.      X  6. 

25.  Under  side  of  another  specimen  showing  lip  more  spreading  near  umbilicus. 

X  6. 

26.  View  of  side  and  aperture.      X  6. 

Ordovician  (Cincinnntian)  Maysville  group,  Cincinnati,  Ohio. 
Fig.  27.  CYCLORA  HOFFMANN:  (Miller)  317 

A  complete  shell.      X 10. 

Ordovician  (Cincinnatian)  Maysville  group,  Cincinnati,  Ohio. 
Figs.  28-30.  CYCLORA  PARVULA  (Hall)  316 

28.  View  of  side  and  aperture.    X  8. 

29.  Under  side  of  shell.     X  8. 

30.  Side  view  of  shell  illustrating  the  characteristic  angulated  first  whorl.     X  8. 

Ordovician  (Cincinnatian)  Maysville  group,  Cincinnati,  Ohio. 
Figs.  31-36.  STROPHOSTYLUS  TEXTILIS  (Ulrich  and  Scofield) 315 

31.  Cast  of  the  interior  showing  the  usual  form  of  the  species. 

32.  Surface  markings  of  a  well  preserved  specimen.     X  5. 

33.  Cast  of  a  depressed  shell  retaining  traces  of  the  external  markings. 

34.  Ventral  view  of  a  testiferous  example. 

35.  Shell  in  which  part  of  the  last  whorl  was  removed  to  show  the  spirally- 

twisted  plates  of  the  columella. 

36.  Dorsal  view  of  the  incomplete  shell. 

Ordovician   (Mohawkian)    Trenton  shales,  St.  Paul,  Minnesota. 
Figs.  37-39.     SINUITES  CANCELLATUS  (Hall)   313 

Three  views  of  an  entire  shell  representing  the  average  proportions  of 
the  Trenton  form  of  the  species. 

Ordovician    (Mohawkian)    Trenton  shales,  Chatfield,  Minnesota. 
Figs.  40,  41     SINUITES  GRANISTRIATCS  (Ulrich)   314 

40.  Dorsal  view  of  an  average  example. 

41.  View  of  aperture  of  another  specimen. 

Ordovician  (Cincinnatian)   Eden  shale,  Covington,  Kentucky. 

Fig.    42.       CONULARIA  TRENTONENSIS    (Hall)     320 

A  nearly  complete  example. 

Ordovician  (Mohawkian)  Trenton  portion  of  Jacksonburg  Is.,  Jackson- 
burg, New  Jersey. 
Fig.  43.     TROCHOLITES  AMMONIUS    (Conrad)    327 

Emmons'  illustration  of  this  species. 

Ordovician  (Mohawkian)  Trenton  Is.,  of  New  York. 

Figs.  1-5  are  after  Hall  and  Clarke;  8-10,  19,  20,  42  are  after  Weller; 
6,  7,  11-13  are  after  Winchell  and  Schuchert ;  14-16  after  Billings;  17, 
18,  31-41  after  Ulrich  and  Scofleld ;  21-26  after  Meek;  and  23  after 
Miller. 

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PLATE  LI 

PAGE 

Figs.  1-3.     SPYROCERAS  BILINEATUM  (Hall)   325 

1.  Apical  portion  of  shell  showing  gradual  development  of  the  annulations.     X  2. 

2.  Fragment  of  small  shell  exhibiting  surface  markings.      X  2. 

Ordovician   (Mohawkian)  Black  River  (Decorah)  shales  of  Minnesota. 

3.  Portion  of  shell  illustrating  appearance  when  broken  out  of  limestone. 

Ordovician  (Mohawkian)   Sinuites  bed  at  base  of  Martinsburg  shale,  1 
mile  south  of  St.  Thomas,  Pennsylvania. 

Figs.  4-7.     ORTHOCERAS  JUNCEUM    (Hall)    323 

4.  Fragmentary  shell  showing  convexity  of  septum  and  a  section  of  the  same 

illustrating  the  central  portion  of  the  siphuncle. 

5.  A   shell  with    the   outer  chamber  well   preserved. 

Ordovician   (Mohawkian)  Trenton  Is.,  Watertown,  New  York. 

6.  Another  fragment  with  the  outer  chamber  and  a  number  of  septa  preserved. 

7.  Outer  chamber  of  another  example,  natural  size. 

Ordovician    (Mohawkian)    Sinuites  bed  at  base  of  Martinsburg  shale, 
1  mile  south  of  St.  Thomas,  Pennsylvania. 

Figs.  8-10.     AMPHILICHAS  TRENTONENSIS   (Conrad)    354 

8.  Dorsal  view  of  a  nearly  complete  cranidium. 

9.  10.     Anterior  and  lateral  views  of  the  same. 

Ordovician    (Mohawkian)    Trenton    portion    of    the    Jacksonburg    Is., 
Jacksonburg,    New  Jersey. 

Fig.   11.     EOHARPES  OTTAWAENSIS    (Billings)    332 

Billings'  illustration  of  a  nearly  complete  example  of  this  fine  species. 
Ordovician   (Mohawkian)   Trenton  Is.,  Ottawa,  Ontario. 

Figs.  12-14.    CYPHASPIS  MATUTINA  (Ruedemann)    353 

12.  Dorsal  view  of  cranidium  of  young  specimen.      X  10. 

13.  Lateral  view  of  same.      X  10. 

14.  Cranidium  of  older  example.      X  5. 

Ordovician    (Mohawkian)    Rysedorph    conglomerate,    Rysedorph    Hill, 
Rensselaer  County,   New  York. 

Fig.  15.     CALYMENE  SENARIA  (Conrad)    357 

Posterior  view  of  pygidium  illustrating  the  usual  part  of  the  trilobite 
found. 

Ordovician  (Mohawkian)  Trenton  portion  of  Jacksonburg  Is.,  Jackson- 
burg,  New  Jersey. 

Fig.  16.     TRIARTHRUS  FISCHERI   (Billings)    341 

Type  specimen.     A  glabella  with  the  fixed  cheeks. 
Ordovician,  Chazyan  of  Newfoundland. 

Figs.  17,  18.     TRIARTHRUS  BECKI   (Green)    342 

Two   specimens  of   average   size  showing  the   characteristic   tubercles 
along  the  median  line  of  the  axis. 

Ordovician   (Cincinnatian)  TJtica  shale  of  New  York. 

Figs.  19,  20.     CRYPTOLITHUS  TESSELATUS   (Green)    335 

Dorsal  and  anterior  view  of  the  head,  the  portion  usually  found. 
Ordovician  (Mohawkian)  Trenton  portion  of  Jacksonburg  Is.,  Jackson- 
burg,    New   Jersey. 

Figs.  21-25.     PROETUS  LATIMARGINATUS  (Weller)   352 

21,  22.   Dorsal  and  lateral  views  of  nearly  complete  cranidium.     X  2. 

23.  Dorsal  view  of  same  specimen. 

24,  25.  A  complete  free  cheek.    Natural  size  and  X  2. 

Ordovician  (Mohawkian)  Trenton  portion  of  Jacksonburg  Is..  Jackson- 
burg,   New   Jersey. 

Figs.  26-29.     ILLAENUS  AMERICANUS  (Billings)    349 

26,  27.  Dorsal  and  front  views  of  the  original  type. 

28.  Pygidium  of  the  same. 

29.  A  complete  example. 

Ordovician   (Mohawkian)   Trenton  Is.,  Ottawa,  Ontario. 

Figs.  30-33.     BUMASTUS  TRENTONENSIS   (Emmons)    351 

30.  Cranidium  of  enrolled  specimen  with  eyes  preserved. 

31.  Pygidium  of  another  enrolled  example. 

32.  A  complete  although  imperfect  extended  specimen  showing  the  characteristic 

eight  segments. 

33.  Cephalon  showing  the  lunate  depressions. 

Ordovician   (Mohawkian)   Trenton  Is.,  near  Watertown.  New  York. 
Figs.  1,  2  are  after  Clarke  ;  4,  5  after  Hall ;  8-10,  15.  19-25  after  Weller  ; 
11.  16,  26-29  after  Billings  ;  12-14  after  Ruedemann. 


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FOSSILS  OF  THE  MARTINSBURG  SHALE   (SINUITES  BED). 


PLATE  LI  I 

PAGE 

Figs.  1,  2.    CORYNOIDES  cALicuLARis  Nicholson , 206 

Nicholson's  figures  of  this  small,  interesting  graptolite. 
Middle  Ordovician  of  Great  Britain. 

Pigs.  3,  4.    CLIMACOGRAPTUS  SPINIFER  (Ruedemann) 203 

Two  rhabdosomes. 

Ordovician  (Cincinnatian),  Utica  shale  of  eastern  New  York. 

Figs.  5-7.    CLIMACOGRAPTUS  PUTILLUS  (Hall) 202 

Three  examples  enlarged  showing  the  characteristics  of  the  species. 
Ordovician  (Cincinnatian),  Utica  shale  of  New  York. 

Figs.  8,  9.    SCHIZOCRANIA  FILOSA  (Hall) 235 

8.  Valve  of  Rafinesquina  alternate/,  with  five  pedicle  valves  of  this 

species  attached.    One  specimen  shows  the  scars  of  the  brachial 
valve. 

9.  Exterior  of  a  brachial  valve  attached  to  Rafinesquina.     X  2. 

Ordovician  (Cincinnatian),  Maysville  group,  Cincinnati,  Ohio. 

Figs.  10-12.    CYCLORA  MINUTA  Hall 316 

Three  views  of  this  dwarfed  gastropod.    X  6. 

Ordovician  (Cincinnatian),  Maysville  group,  Cincinnati,  Ohio. 

Fig.  13.    LEPTOBOLUS  INSIGNIS  Hall Z31 

Exterior  of  the  shell  showing  the  concentric  and  radiating  striae. 
X8. 

Ordovician    (Cincinnatian),   Utica   shale,   Middleville,   New 
York. 

Figs.  14-16.    BYTHOCYPRIS  CYLINDRICA  (Hall) 371 

Side  and  two  edge  views  of  a  complete  carapace.    X  20. 

Ordovician  (Cincinnatian),  Eden  shale,  Cincinnati,  Ohio. 

Fig.  17.    CRYPTOLITHUS  TESSELLATUS  Green 335 

Diagrammatic  drawing  of  an  entire  specimen. 
Upper  Ordovician  of  Canada. 

Figs.  18-20.    TRIARTHRUS  BECKI  Green 342 

Outline  drawings  of  three  specimens. 

Ordovician  (Cincinnatian),  Utica  shale,  New  York. 

Figs.  21-23.    CARYOCARIS  SILICULA  Bassler  n.  sp 372 

21.  Valve  of  this  crustacean,  imperfect  at  one  end.    X  3. 

22.  A  less  complete  example.    X  3. 

23.  A  specimen  representing  the  opposite  valve.     X  3. 

Ordovician   (Mohawkian),  lower  beds  of  Martinsburg  shale, 
Strasburg,  Virginia. 

Figs.  24,  25.    LEPIDOCOLEUS  JAMESI  (Hall  and  Whitfield) 371 

Detached  plates,  enlarged. 

Ordovician  (Cincinnatian),  Eden  shale,  Cincinnati,  Ohio. 
Figs.  1,  2  are  after  Nicholson;  3-7  after  Ruedemann;  8,  9,  24, 
25  after  Hall  and  Whitfield;  14-16  after  Ulrich;  and  13  after  Hall 
and  Clarke. 


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FOSSILS  OF  THE  MARTINSBURG  SHALE   (CORYNOIDES  BED) . 


PLATE  LIII 

PAGE 

Fig.  1.    CLIMACOGRAPTUS  BICORNIS  (Hall) 204 

Typical  specimen  showing  sicular  extremity. 

Ordovician  (Crazyan),  Normanskill  shale,  Kenwood,  New 
York. 

Figs.  2-4.    DIPLOGRAPTUS  VESPERTINUS  Ruedemann 205 

2.  Early  form  of  the  species.     X  5. 

3.  Late  type.     X  5. 

4.  Enlargement  of  a  larger  specimen.    X  5. 

Ordovician  (Chazyan),  Normanskill  shale,  Van  Schaick 
Island,  New  York. 

Fig.  5.    MEROCRINUS  sp 211 

Several  segments.     X  4. 

Ordovician  (Cincinnatian),  Eden  portion  of  Martinsburg 
shale,  one  and  one-half  miles  northeast  of  Fort  London,  Pennsyl- 
vania. 

Figs.  6,  7.    HETEROCRINUS  HETERODACTYLUS  Hall 210 

6.  An  example  preserving  the  body  and  a  part  of  the  column. 

7.  Portion  of  the  same  enlarged. 

Ordovician  (Cincinnatian),  Eden  shale,  Cincinnati,  Ohio. 

Fig.  8.     HUDSONASTER  CLARKi  Bassler,  n.  sp 211 

Photograph  of  a  gutta-percha  squeeze  of  the  two  type  specimens  pre- 
served as  a  mold  in  sandy  shale.     X  4. 

Ordovician  (Cincinnatian),  Eden  portion  of  the  Martinsburg 
shale,  one  and  one-half  miles  northeast  of  Fort  Loudon,  Pennsyl- 
vania. 

Fig.  9.    BERENICEA  VESICULOSA  Ulrich 214 

Surface  of  the  type  specimen.     X  18. 

Ordovician  (Cincinnatian),  Eden  shale,  Cincinnati,  Ohio. 

Fig.  10.     HALLOPORA  OXEALLI  SIGILLARIOIDES   (Nicholson) 222 

A  fragment  of  sandstone  with  several  molds  of  this  abundant  species. 
Ordovician  (Cincinnatian),  Eden  portion  of  the  Martinsburg 
shale,  one  and  one-half  miles  northeast  of  Fort  Loudon,  Pennsyl- 
vania. 

Figs.  11-13.     BYTHOPORA  ARCTIPORA  (Nicholson) 221 

11, 12.  Fragment  of  the  cylindrical  zoarium,  natural  size  and  a  portion 
enlarged. 

13.  Several  zooecia  much  enlarged. 

Ordovician  (Cincinnatian),  Eden  shale,  Cincinnati,  Ohio. 

Figs.  14, 15.    ARTHROPORA  CLEAVELAXDI  (James) 225 

14.  Three  segments.     X  4. 

15.  Portion  of  a  segment.     X  18. 

Ordovician  (Cincinnatian),  Eden  shale,  Cincinnati,  Ohio. 
Figs.  1-4  are  after  Ruedemann;   6,  7,  after  Meek;   and  11-15 
after  Nicholson. 

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PLATE  LIV 

PAGE 

Figs.  1,  2.     BATOSTOMA  JAMESI    (Nicholson)    220 

1.  Zoariuni  natural  size. 

2.  Surface  of    same    enlarged,    showing    rounded    cells    with    thick    wall    and 

numerous  acanthopores. 

Ordovician  (Cincinnatian)  Eden  shale,  Cincinnati,  Ohio. 

Pigs.  3,  4.     RAFINESQUINA  SQUAMULA   (James)    264 

Two  examples,  each  showing  the  pedicle  valve. 
Ordovician   (Cincinnatian)   Eden  shale,  Cincinnati,  Ohio. 

Figs.  5,  6.     DALMANELLA  MULTISECTA  (Meek)    244 

5.  Pedicle  valve. 

6.  Interior  of  brachial  valve. 

Ordovician   (Cincinnatian)   Eden  shale,  Cincinnati,  Ohio. 

Figs.  7-9.     STOPHOMENA  HALI.IE  (Miller)    251 

7.  Interior  of  pedicle  valve. 

8.  Brachial  valve. 

9.  Interior  of  brachial  valve. 

Ordovician   (Cincinnatian)   Eden  shale,  Cincinnati,  Ohio. 

Figs.  10-14.     STROPHOMENA  SINUATA   (James)    252 

10-11.   Interior  of  the  brachial  and  pedicle  valves. 
12-14.  Anterior  view  and  the  two  sides  of  a  specimen. 

Ordovician   (Cincinnatian)   Maysville  group,  Cincinnati,  Ohio. 

Figs.  15,  16.     PLECTORTHIS  PLICATELLA  (Hall)    242 

Brachial  valve  and  interior  of  the  same  valve  of  another  example. 
Ordovician  (Cincinnatian)  Maysville  group,  Cincinnati,  Ohio. 

Figs.  17-19.     CTENOOONTA  OBLIQUA   (Hall)    278 

Views  of  two  shells  and  the  cardinal  side  of  one.     X  10. 
Ordovician    (Cincinnatian)    Maysville  group,  Cincinnati,  Ohio. 

Figs.  20-22.     ZYGOSPIRA  MODESTA   (Hall)    274 

Opposite  sides  and  edge  view  of  this  small  brachiopod. 
Ordovician   (Cincinnatian)   Maysville  group,  Cincinnati,  Ohio. 

Figs.  23,  24.     PHOLIDOPS  CINCINNATIENSIS   (Hall)    236 

Brachial  valve  and  profile  of  the  same.      X  3. 

Ordovician   (Cincinnatian)  Maysville  group,  Cincinnati,  Ohio. 

Fig.  25.     LEPTAENA  GIBBOSA  (James)    259 

Pedicle  valve  of  a  specimen  identified  by  the  author  of  the  species. 
Ordovician   (Cincinnatian)   Eden  shale,  Cincinnati,  Ohio. 

Figs.  26-29.    CTENODONTA  FILISTRIATA  (Ulrich) 279 

26.  Left  valve. 

27.  Right  side  of  cast  of  interior. 

28.  Cardinal  view  of  left  valve. 

29.  Portion  of  surface  of  shell,  highly  magnified. 

Ordovician   (Cincinnatian)   Eden  shale,  Cincinnati,  Ohio. 

Fig.  30.     LYRODESMA  CONRADI  (Ulrich)    286 

Cast  of  the  interior  showing  the  muscular  scars  and  the  sinuate  pallial 
line. 

Ordovician   (Cincinnatian)   Eden  shale,  Cincinnati,  Ohio. 

Figs.  31-33.     PLECTAMBONITES  RUGOSUS  (Meek)   255 

31,  32.  Pedicle  and  brachial  valves. 

33.  Interior  of  the  brachial  valve. 

Ordovician   (Cincinnatian)   Eden  shale,  Cincinnati,  Ohio. 

Figs.  34-36.     BYSSONYCHIA  VERA   (Ulrich)    282 

34,  35.  Left  side  and  anterior  view  of  a  partial  cast  of  the  interior. 
36.  Well  preserved  cast  of  the  interior  snowing  muscular  impressions. 

Ordovician   (Cincinnatian)   Eden  shale,  Newport,  Kentucky. 

Fig.  37.     CLIDOPHORUS  PLANCLATUS  (Conrad)    280 

Shell  of  this  species  on  slab  with  Plectambonites. 
Ordovician   (Cincinnatian)   Pulaski  shales  of  New  York. 
Figs.  1.  2  are  after  Nicholson  ;  5,  6,  10-24  after  Meek  ;  7-9  after  Miller  ; 
and  26-30,  34  after  Ulrich. 


404 


MARYLAND  GEOLOGICAL  SURVEY 


CAMBRIAN  AND  ORDOVICIAN,   PLATE  LIV 


34  35  37 

FOSSILS  OF  THE  MARTINSBURG  SHALE  (EDEN  DIVISION). 


PLATE  LV 

PAGR 

Figs.  1-4.     LEPIDOCOLEUS  JAMESI  (Hall  and  Whitfleld) 371 

1.  Sketch  showing  the  plates  in  position. 

2,  3.  Detached  plates  enlarged. 

Ordovician  (Cincinnatian),  Eden  shale,  Cincinnati,  Ohio. 

4.  A  broader  plate  referred  to  this  species.     X  10. 

Ordovician    (Mohawkian),  Trenton  Is.,  Trenton  Falls,  New 
York. 

Figs.  5,  6.    LOPHOSPIRA  (RUEDEMANNIA)  LIRATA  Ulrich 295 

5.  A  specimen  with  numerous  spiral  ridges  on  the  basal  part  of  the 

volutions. 

6.  Portion  of  the  lower  part  of  the  last  whorl  of  same  including  the 

band.     X  3. 

Ordovician  (Cincinnatian),  Eden  shale,  Newport,  Kentucky. 

Figs.  7,  8.     HORMOTOMA  GRACILIS  (Hall) 292 

View  natural  size,  and  a  portion  enlarged,  of  the  typical  form  of  this 
species. 

Richmond   (Maquoketa)  shale,  Graf,  Iowa. 

Figs.  9-11.    SINUITES  GRANISTRIATUS  (Ulrich) 314 

9.  Lateral  view  of  a  specimen. 

10.  Dorsal  view  of  an  average  example. 

11.  Apertural  view  showing  form  of  mouth  and  extent  of  the  gran- 

ostriate  expansion. 
Ordovician  (Cincinnatian),  Eden  shale,  Covington,  Kentucky. 

Figs.  12-21.    SINUITES  CANCELLATUS  (Hall) 313 

12, 13.  Two  views  of  a  cast  of  the  interior  showing  strong  wrinkles  of 

growth  near  the  aperture. 

14.  Apertural  view  of  shell  with  mouth  less  expanded  than  usual. 
15. 16.  Two  views  of  a  small  cast. 

Ordovician   (Mohawkian),  Black  River  and  Trenton  forma- 
tions of  Minnesota. 

17.  Dorsal  view  of  a  globose  variety. 

18.  Surface  of  left  lobe  of  outer  lip.    X  4.5. 

Ordovician  (Cincinnatian),  Eden  shale,  Covington,  Kentucky. 
19-21.  Three  views  of  an  average  entire  shell. 

Ordovician   (Mohawkian),  Trenton  shales,  Chatfleld,  Minne- 
sota. 

Figs.  22-24.    TETRANOTA  OBSOLETA  Ulrich 310 

Three  views  of  the  type. 

Ordovician    (Mohawkian),  Trenton  shale,  Goodhue  County, 
Minnesota. 

Figs.  25,  26.    LIOSPIRA  MICULA  (Hall) 296 

Two  views  of  a  nearly  perfect  example. 

Ordovician  (Cincinnatian),  Eden  shale,  Covington,  Kentucky. 

Fig.  27.    ORTHOCERAS  TRANSVERSUM  Miller 324 

Type  specimen,  showing  the  transverse  surface  markings. 

Ordovician  (Cincinnatian),  Eden  shale,  Cincinnati,  Ohio. 

Figs.  28-31.    BYTHOCPRIS  CYLINDRICA  (Hall) 371 

28,  30,  31.  Views  of  a  complete  carapace.     X  20. 

29.  Interior  of  a  right  valve.     X  20. 

Ordovician  (Cincinnatian),  Eden  shale,  Cincinnati,  Ohio. 

Fig.  32.    ULRICHIA  BIVERTEX  (Ulrich) 370 

Right  valve  showing  the  two  prominent  nodes.     X  20. 

Ordovician     (Mohawkian),     Trenton     shales,     Montgomery 
County,  New  York. 

Fig.  33.    APARCHITES  MINUTISSIMUS  (Hall) 366 

Valve  highly  magnified. 

Ordovician  (-Cincinnatian),  Eden  shale,  Cincinnati,  Ohio. 

Fig.  34.     CERATOPSIS  CHAMBERSI  (Miller) 369 

Valve  illustrating  the  prominent  spine.    Highly  magnified. 

Ordovician  (Cincinnatian),  Eden  shale,  Cincinnati,  Ohio. 
Figs.  1-3,  33,  34,  are  after  Hall  and  Whitfield;    6,  32  after 
Ruedemann;  4-26  after  Ulrich  and  Scofield;  27  after  Miller;  and 
28-31  after  Ulrich. 

405 


"MARYLAND  GEOLOGICAL  SURVEY 


CAMBRIAN  AND  ORDOVICIAN,  PLATE  LV 


FOSSILS  OF  THE  MARTINSBURG  SHALE  (EDEN  DIVISION). 


PLATE  LVI 

PAGE 

Figs.  1,  2.    CALYMENE  GRANULOSA  Foerste 356 

1.  An  entire,  extended  specimen. 

2.  Portion  of  same  showing  granulose  surface.     X  4. 

Ordovician  (Cincinnatian),  Eden  shale,  Cincinnati,  Ohio. 

FIGS.  3,  4.     ISOTELUS  STEGOPS   Green 342 

3.  A  complete  although  somewhat  imperfect  example. 

4.  The  spinose  form  of  the  species. 

Ordovician  (Cincinnatian),  Eden  shale,  Cincinnati,  Ohio. 

Figs.  5,  6.    CBYPTOLITHUS  BELLULUS  (Ulrich) 333 

5.  Cephalon  with  spines  preserved. 

6.  The  original  type  representing  the  young  form  of  the  species.    X  3. 

Ordovician  (Cincinnatian),  Eden  shale,  Covington,  Kentucky. 

Figs.  7-13.    TRIARTHUS  BECKI  Green 342 

7-11.  Specimens  in  various  stages  of  growth. 

12, 13.  Drawings   of   Beecher's   celebrated   restorations   showing   the 
appendages  in  position. 

Ordovician  (Cincinnatian),  Utica  shale,  New  York. 

Figs.  14-17.    CRYPTOLITHUS  RECURVUS  (Ulrich)  n.  sp 334 

14, 15.  Two  imperfect  but  almost  entire  specimens. 

Ordovician  (Cincinnatian),  Eden  shale,  Covington,  Kentucky. 

16.  Cephalon  showing  convexity. 

17.  Pygidium. 

Ordovician  (Mohawkian),  Trenton  Is.,  Covington,  Kentucky. 

Fig.  18.    CORNULITES  FLEXUOSUS  Hall 276 

A  group  of  tubes  adhering  to  a  brachiopod  shell. 

Ordovician  (Cincinnatian),  Maysville  group,  Cincinnati,  Ohio. 


406 


MARYLAND  GEOLOGICAL  SURVEY 


CAMBRIAN  AND  ORDOVICIAN,  PLATE  LVI 


16 


FOSSILS   OF   THE    MARTINSBURG  SHALE    (EDEN   DIVISION), 


PLATE  LVII 

PAGE 

Figs.  1-3.    LINGULA  NICKLESI  Bassler  n.  sp 232 

I,  2.  Two  examples,  one  partly  exfoliated. 

3.  View  of  specimen  shown  in  Fig.  1.     X  4. 

Ordovician  (Cincinnatian),  Maysville  group,  Fairview  forma- 
tion, Cincinnati,  Ohio. 

Figs.  4-7.    PLECTORTHIS  PLICATELLA  (Hall) 241 

4,  5.  Front  and  interior. 

6,  7.  Cardinal  and  profile  views  of  shell. 

Ordovician  (Cincinnatian),  Maysville  group,  Fairview  forma- 
tion, Cincinnati,  Ohio. 

Fig.  8.    RAFINESQUINA  ALTEBNATA  (Emmons) 265 

Pedicle  valve  of  the  usual  Maysville  form  of  the  species. 

Ordovician  (Cincinnatian),  Maysville  group,  Cincinnati,  Ohio. 

Figs.  9-12.    OBTHOBHYNCHULA  LINNEYI  (James) 271 

9, 10.  Dorsal  and  ventral  views  of  an  average  specimen. 

II.  Central  portion  of  cardinal  region  showing  distinct  cardinal  area 

and  open  delthyrium.     X  3. 
12.  Profile  views  of  shell  natural  size. 

Ordovician  (Cincinnatian),  Maysville  group,  Nashville,  Ten- 
nessee. 

Figs.  13-16.     ZYGOSPIBA  MODESTA  Hall 274 

Dorsal,  ventral,  edge,  and  side  views  of  an  example  of  this  abundant 
brachiopod. 
Ordovician  (Cincinnatian),  Maysville  group,  Cincinnati,  Ohio.  . 

Figs.  17-23.    ZYGOSPIBA  EBBATICA  Hall 275 

17.  A  small  example. 

18.  Profile  view  of  moderately  convex  specimen. 

19.  Front  view  of  another  specimen. 

20.  21.  Opposite  sides  of  cast  of  a  large  example. 
22.  Cardinal  view  of  large  specimen. 

Ordovician  (Cincinnatian),  Pulaski  shales  of  New  York. 

Fig.  24.     PTEBINEA  DEMISA  (Conrad) 284 

Left  valve,  natural  size. 

Ordovician  (Cincinnatian),  Maysville  group,  Cincinnati,  Ohio. 

Fig.  25.    MODIOLODON  TBUNCATUS  (Hall) 288 

Left  side  of  a  cast  of  the  interior,  showing  usual  aspect  of  the  species. 
Ordovician    (Cincinnatian),  Maysville  group,  McMillan  for- 
mation, Cincinnati,  Ohio. 

Fig.  26.    BYSSONYCHIA  BADIATA  (Hall) 282 

Left  valve  of  the  usual  size. 

Ordovician  (Cincinnatian),  Maysville  group,  Fairview  for- 
mation, Cincinnati,  Ohio. 

Fig.  27.    ALLONYCHIA  OVATA  Ulrich 284 

Left  valve,  natural  size. 

Ordovician  (Cincinnatian),  Maysville  group,  Fairview  forma- 
tion, Covington,  Kentucky. 

Figs.  28,  29.    BYSSONYCHIA  PBAECUBSA  Ulrich 283 

28.  Cast  of  interior  of  right  valve. 

29.  Anterior  view  of  shell  showing  the  byssal  opening. 

Ordovician  (Cincinnatian),  Lorraine  shales,  Lorraine,  New 
York. 

Figs.  4-8,  13-16  after  Meek;  17-23  after  Hall;  9-12  after  Hall 
and  Clarke;  24,  26  after  Hall  and  Whitfield;  and  25,  27-29  after 
Ulrich. 

407 


MARYLAND  GEOLOGICAL  SURVEY 


CAMBRIAN  AND  ORDOVICIAN,  PLATE  LVII 


FOSSILS  OF  THE  MARTINSBURG  SHALE   (MAYSVILLE  DIVISION). 


PLATE  LVIII 

PAGE 

Fig.  1.    ORTHODESMA  NASUTUM  Conrad 289 

A  fairly  well  preserved  right  valve  showing  the  narrow,  extended, 
nasute  form. 

Ordovician  (Cincinnatian),  Orthorhynchula  bed  at  top  of 
Fairview  formation,  Tuscarora  Mountain,  one  and  one-half 
miles  southeast  of  McConnellsburg,  Pennsylvania. 

Figs.  2,  3.     ISCHYBODONTA  UNioNoiDES   (Meek) 281 

2.  Right  valve  of  an  example  presenting  the  test. 

3.  Impressions  of  inner  side  of  a  right  valve  showing  the  anterior 

muscular  scar. 

Ordovician  (Cincinnatian),  top  of  Fairview  or  base  of 
McMillan  formation,  Covington,  Kentucky. 

Fig.  4.    RAFINESQUINA  SQUAMULA  (James) 264 

Impression  of  the  shell  in  sandstone. 

Ordovician  (Cincinnatian),  Orthorhynchula  bed  at  top  of 
Fairview  formation,  Tuscarora  Mountain,  one  and  one-half 
miles  southeast  of  McConnellsburg,  Pennsylvania. 

Figs.  5,  6.    ORTHOCEBAS  LAMELLOSUM  Hall 324 

5.  View  showing  separation  of  septa  and  other  characters  of  the  shell. 

6.  View  illustrating  position  of  the  siphuncle. 

Ordovician  (Cincinnatian),  Pulaski  shales  near  Pulaski, 
New  York. 

Figs.  7-9.     LIOSPIBA  MICULA  (Hall) 296 

Top,  bottom,  and  side  views  of  a  nearly  perfect  example. 

Ordovician  (Cincinnatian),  Eden  shale,  Covington,  Kentucky. 

Figs.  10,  11.    ISOTELUS  MEGISTOS  Locke 343 

10.  Meek's  type  of  Asaphus  megistos  Locke  (Pal.  Ohio,  Vol.  1,  pi.  14, 

fig.    13)    enlarged    one-third,    representing    the    spinous    form 
(?  male). 

Ordovician  (Cincinnatian),  near  top  of  Fairview  formation, 
Cincinnati,  Ohio. 

11.  Hypostoma  of  a  larger  example. 

Ordovician  (Cincinnatian),  lower  part  of  McMillan  forma- 
tion, Morrow,  Ohio. 

Fig.  12.    MODIOLOPSIS  MODIOLARIS  (Conrad) 286 

One  of  Hall's  original  figures  which  well  represents  the  usual  aspect 
of  the  species.    It  illustrates  a  slightly  compressed  right  valve. 
Ordovician    (Cincinnatian),    Pulaski    shales    near    Pulaski, 
New  York. 

Figs.  2,  3,  7-9  are  after  Ulrich  and  5,  6,  12  after  Hall. 


408 


MARYLAND  GEOLOGICAL  SURVEY 


CAMBRIAN  AND  ORDOVICIAN,   PLATE  LVIII 


FOSSILS  OF  THE  MART1NSBURG  SHALE   (MAYSVILLE  DIVISION). 


GENERAL  INDEX 


Abbe,  Cleveland,  Jr.,  42. 
Acadian  fossils,   89. 
Adirondack  uplift,  74. 
Aikin,  W.  E.  A.,  35. 
Alabama,  23,  83,  118,   136. 
Ale,  Myra,  8. 
Alexander,  J.  H.,  35. 
Algae,  Calcareous,  82. 

Proterozoic  forms  of,  85. 
Allegheny  Plateau,   23. 
Amsterdam,  N.  Y.,  fossils  from,  192. 
Antietam  battle-field,   70,  80. 
Antietam  Creek,  57. 
Antietam  sandstone,   48,   54,   57,   58,   59, 

65,  88,  89. 

Composition  of,  58. 
Antietam  Station,  85. 
Appalachian  Region,  23,  60,  88. 
Appalachian   Valley,   60,   61,   67,  76,   83, 

85,  89,  90,  101,  106,  107,  109,  110,  114, 

116,  118,  126,  129,  132,  154,  156,  160, 

161,  167,  191. 
Fossils   from,    190,    196,    201,    202,    206, 

208,  241,  245,  257,  292,  300,  308,  315, 

360. 
Axeman   limestone,    101. 

B 

Bain,  H.  F.,  87. 

Bassler,  R.  S.,  11,  13,  23,  42,  43,  185,  187. 
Bear  Pond  Mountain,  172. 
Beaver  Creek,  65,  70. 
Beekmantown  formation,   103,   117,   140. 
Beekmantown  limestone,  48,  76,   80,   82, 
87,  89,  114,  115,  116,  123. 

Areal  distribution.  109. 

Faunal  zones,  96. 

Generalized  section  of,  93. 

Lithologic  character  of,  92. 

Residual  products  of,  105. 

Section  of,  94. 

Topography  of,  105. 
Beekmantown»-Conococheague     boundary, 

103. 

Bellefonte,  Pa.,  Fossils  from,  347. 
Belief onte  dolomite,   101. 
Benevola,  65,  70. 
Berry,  E.  W.,  7. 

29 


Billings,  E.,  196,  308,  341. 

cited,  309,  319,  333,  337,  350. 
Birdseye  limestone,  27. 
Bissel,  99. 

Black  River,  117,  129,  136,  141,  154. 
Black    River    group,    Fossils    from,    195, 

199,  202,  213,  219,  226,  227,  249,  263, 

273,  315,  326,  330,  349,  359. 
Blue  Ridge,  61,  65,  67,  90,  132. 

Fossils  from,  277. 
Blue  Ridge  District,  23. 
Blue  Ridge  Province,  56,  58. 
Blue  Springs,  Fossils  from,  193,  198,  208, 

209,  224,  226,  227,  238,  239,  240,  258, 

261,  271. 

Boonsboro,  59,  65. 
Bostetter,   123. 
Bowman's  Mill,  81. 
Brachiopods,  71,  82,  83,  97,  99,  100,  113, 

135,  142. 
Braddock,  114. 
Brown,  T.  C.,  44,  87. 
Buena  Vista  shale,   67. 
Burnside  Bridge,  70. 
Butts,   Charles,  88. 


Calcareous  algae,  82. 
Cambria,  Wales,  25. 
Cambrian,  23,  25. 

Columnar  sections  of,  48,  49. 

Correlation  table  of,  51. 

Geology  of,  24. 

History  of,  25. 

Paleogeography   of,   45. 

Paleontologic    characteristic   of,    50. 

Physiography  of,  23. 

Stratigraphic  characteristics  of,  50. 
Cambrian  age,  Fossils  of.  88. 
Cambrian-Ordovician  limestones.  60. 

Table  of,  60. 

Thickness  of,  60. 
Campbell,  H.  D.,  67. 
Canada,  23,  136. 

Fossils    from,    202,    224,    231,    232, 
238,  239,  248,  269,  277,  278,  282,  283, 
285,  298,  302,  309,  326,  350,  359. 
Canadian  system,   30,   31. 
Cannjoharie,    N.    Y.,    Fossils   from,    192, 
303,  304. 


410 


Canu,  Ferdinand,  45. 
Caradoc  Group,  25. 
Carlisle,   Pa.,   120. 

Fossils  from,  306,  355. 
Caryocystites  bed,  133,  136,  148,  149,  150, 
151,  152,  154. 

Fauna  of,  135. 
"  Cauliflower  "   chert,   117. 
Catoctin  Mountain,   53,  56,   58,   59,   110, 

111,  113. 

Catoctin  schist,  54. 
Cavetown,  61,  62,  70. 
Cearfoss,  147. 

Central  Basin,  Tennessee,  127. 
Cephalopods,  98,  99,  113,  115,  144. 
Ceratopea  zone,  93,  96,  103. 

Fossils  of,  104. 

Chambersburg,    Pa.,    94,    120,    124,    130, 
131,  140,  143,  144,  153. 

Fossils  from,  166,  197,  203,  206, 
215,  231,  232,  235,  238,  239,  243, 
269,  295,  306,  310,  312,  315,  316, 
317,  320,  321,  323,  326,  327,  333, 
336,  338,  341,  342,  350,  351,  353, 
354,  355,  356,  357,  362,  373. 

Section  1  mi.  east  of,  94. 
Chambersburg   limestone,    49,    117,    129, 
145,  146,  147,  148,  149,  150,  151,  152, 
153,  157. 

Age  of,  153, 

Areal  distribution  of,   132. 

Correlation  of,  153. 

Distribution  of  beds  of,  152. 

Divisions  of,  154. 

Faunal  zones  of,  132. 

Lithologic  character  of,  130. 

Sections  of,  144. 

Thickness  of,  131. 
Chambersburg  quadrangle,  57. 

Fauna  of,  164. 

Chambersburg-Gettysburg  Pike,  94. 
Champlain  Region,  120. 
Champlain  Valley,  87,  90. 

Faunas  of,  127. 
Charlton,  80,  86,  102,  103. 

Fossils  from,  302. 
Chazy  formation,  112. 
Chazyan  age,  115,  117,  129. 
Chazyan  limestones,  27,  120. 
Chazyan  shales,  Fossils  from,  206. 
Chewsville,  65,  70,  73,  81,  82,  85. 
Christiania  bed,  133,  140,  142,  143,  144, 
145,  146,  147,  152,  153. 

Fauna  of,  143. 
Christiania  zone,  144. 
Cincinnati,  Ohio,  Fossils  from,  242,  251, 

280,  282,  286,  324,  356. 
Cincinnatian  series,  30,  156. 
Clark,  William  Bullock,  19,  41,  42,  212. 
Clarke,  J.  M.,  170,  272. 


Cleland,  H.  F.,  303. 

Clinton  formation,  170. 

Coastal  Plain,  23. 

Collingwood  shale,  267. 

Colorado,  Fossils  from,  238. 

Columbia,  Fossils  from,  247. 

Conococheague  Creek,  76,  132,  139,  141, 

150,  151,  156,  158,  161,  217. 
Conococheague  limestone,  48,  65,  72,  73, 
74,  88,  89,  90,  92,  98,  106,  110. 

Age  of,  82. 

Areal  distribution  of,  81. 

Correlation  of,  82. 

Cryptozoon  reefs  of,  83. 

Edgewise  conglomerate  of,  86. 

Fossils  of,  88. 

General  section  of,  78. 

Section  of,  77. 

Topography  of,  81. 
Contents,  11. 
Coplay  limestone,  100. 
Corynoides  bed,  158. 

Fauna  of,  167. 
Cowans  Gap,  168. 

Fossils  from,  169,  221,  222,  237,  296, 

311,  334,  356. 
Covington,  Ky.,  Fossils  from,  284,   312, 

334,  335. 

Crown  Point  limestone,  120,  126. 
Cumberland  Valley,  24,  76,  129,  191. 
Cumberland   Valley   Railroad,    103,    123, 

360. 

Gushing,  H.  P.,  74. 
Crinoid  plates,  143. 
Cryptozoon  reefs,  78,  83. 
Cryptozoon  steeli  zone,  93,  96,  101,  103, 
107,  191. 

Fossils  of,  102. 


Dana,  James  D.,  38,  45. 
Decorah  shales,  139,  141. 

Fossils  from,  197,  217,  224,  258. 
Dickey,  Pa.,  Section  N.  W.  of,  148,  149. 
Distribution  of  fauna,  Tables  of,  174. 
Dorsey,  C.  W.,  41. 
Ducatel,  J.  T.,  35,  36. 


Eakles  Mills,  59,  65. 

Fossils  from,  234,  277,  319,  339. 
Eaton,  H.  N.,  44. 

Echinospherites  bed,  132,  133,  139,  144, 
145,  146,  150,  151,  152,  153,  154. 

Fauna  of,  139. 
Eden  age,  156,  163. 
Eden  division,  157,  158. 

Fossils  of,  167,  169. 


GENERAL  INDEX 


411 


Eden  formation,  Fossils  of,   169. 

Eden  shale,  Fossils  from,  211,  214,  255, 

260,  324,  334,  356. 
Edgewise  conglomerate,  86. 
Elbrook  formation,  48,  63,  65,  70,  72,  80, 
81. 

Age  of,  74. 

Areal  distribution  of,  72. 

Correlation  of,  74. 

Lithologic  character  of,  72. 

Residual  products  of,  73. 

Thickness  of,  72. 

Topographic  form  of,  73. 
Elbrook  limestone,  76,  83,  88,  89. 
Elk  Ridge,  53,  56,  58,  59. 
Emmons,  S.  F.,  27. 
Eopaleozoic,   30. 

Esthonia,  Russia,  Fossils  from,  218,  228. 
Etheridge,  Robert,  45. 


Fairview  formation,  171,  272. 
Fairview  Mountain,  172. 

Fossils  from,  225,  275,  371. 
Foerste,  A.  F.,  255,  265,  280,  285,  287. 
Fontaine,  W.  M.,  37. 
Fort  Cassin,  Fossils  from,  327,  332. 
Fort  Hunter,  Fossils  from,  247,  304,  306, 

362. 
Fort  Loudon,  148,  149,  160,  168. 

Fossils  from,  193,  197,  198,  199,  201, 
202,  205,  208,  209,  210,  211,  212, 
214,  221,  222,  225,  226,  227,  228, 
237,  238,  239,  240,  242,  245,  251, 
253,  255,  258,  260,  261,  265,  271, 
273,  276,  278,  279,  280,  286,  292, 
296,  297,  300,  301,  309,  311,  315, 
324,  328,  334,  335,  342,  343,  356, 
359,  365,  366,  367,  368,  369,  370, 
372. 

Section  %  mi.  south  of,  150. 
"  Fossiliferous  graywacke  series,"  25. 
Frazer,  Persifor,  Jr.,  37,  38,  39. 
Frederick,  114,  115,  116. 

Fossils  from,  209,  250,  322,  345,  356. 
Frederick  limestone,  115. 
Age  of,  117. 
Fossils  of,  116. 
Thickness  of,  116. 
Frederick  Valley,  24,  90,  109,  110,  111, 

113,  114,  115,  116. 
Frederick  Valley  limestones,  111. 
Age  of,  113. 
Description  of,  111. 
Extent  of,  111. 
Structure  of,   113. 
Fruitville.   66. 
Fucoids,   99. 


Funkstown,  97. 

Fossils  from,  190,  238,  247,  303,  304, 
306,  307,  329,  330,  332,  348,  352. 


Gatesburg  dolomite,  83. 

Gastropods,    94,    98,    99,    100,    103,    104, 

122,  128,  137,  163. 
Geiger,  H.  R.,  32,  39. 
Goodnow,  Frank  J.,  5. 
Grabau,  A.  W.,  87. 
Grasty,  J.  S.,  43. 
Great  Valley,  24,  32,  73,  76,  81,  172. 

Elevation  of,  24. 

Extent  of,  24. 
Greater  Appalachian  Valley,  23. 

Division  of,  23. 
Greencastle,  Pa.,  120. 

Fossils  from,  224,  274,  323,  330. 

Section  at,  147. 

Greencastle  bed,  133,  140,  141,  143,  144, 
145,  146,  147,  152,  153,  154. 

H 

Hagerstown,  62,  73,   81,  82,   85,   98,  99, 
103,  107,  110,  126. 

Fossils  from,  191,  192,  196,  200,  246, 
247,  267,  291,  297,  299,  303,  304, 
305,  306,  307,  322,  340,  346,  347, 
348,  362,  363. 

Hagerstown  Valley,  24,  57,  65,  73,  80. 
•General    section    of    Conococheague 

limestone  in,  78. 

Hagerstown-Frederick  trolley  road,  64. 
Halfway,  103. 

Fossils  from,  246,  290,  292,  300,  341, 

360. 
Hall,  James,  202,  323,  325. 

Cited,  189,  199,  201,  210,  242,  266, 
272,  274,  275,  276,  283,  285,  288, 
298,  317,  323,  327,  339,  342,  367, 
370,  371,  372. 
Harmony  Hill  School,  65. 
Harper's  Ferry,  54,  57,  58. 
Harpers  schist,  88. 

Harpers  shale,  48,  54,  57,  58,  59,  61,  65, 
89,  113,  114. 
Outcrop  of,  58. 
Thickness  of,  57. 
Harrington,  Emerson  C.,  5,  9. 
Harrisburg,  Pa.,  120. 
Hayes,  C.  W.,  117. 
Highbridge,  Ky.,  118. 
Highgate  Springs,  Fossils  from,  244. 
Historical  Review,  25. 
Hitchcock,  E.,  36. 
Hoosac  Mountains,  27. 
Hoyt  limestone,  74. 

Fossils  from,  190,  191. 


412 


Hudson  River  formation,  112. 
Hudson  River  shale,  27,  113. 
Hunt,  T.  Sterry,  37,  45. 
Huyett,  105. 

Fossils  from,  291,  293,  294,  299,  302, 
327,   331,   364. 

I 

Illinois,  Fossils  from,  320. 
Illustrations,  15. 
Introduction,  23. 
Iowa,  Fossils  from,  268,  320. 


James,  U.  P.,  cited,  260. 

Jandorf,  M.  L.,  44. 

Jefferson,  Thomas,  34. 

Jordan  Knob,  Pa.,  168. 

Fossils  from,  169,  205,  210,  211,  212, 
214,  221,  222,  225,  237,  242,  245, 
251,  253,  255,  260,  265,  276,  279, 
280,  286,  296,  297,  311,  315,  324, 
334,  335,  343,  356,  367,  370,  372. 

Juniata  formation,  49,  156,  157,  168,  170. 

Juniata  shales,  161. 


K 

Kauffman,  Pa.,  123,  139. 

Fossils  from,  231. 
Keedysville,  58,  60. 

Keith,  Arthur,  32,  34,  39,  40,  57,  59,  67. 
Kentucky,  315,  327. 

Fossils  from,  195,  197,  224,  230,  272, 

300,  301,  309,  315,  327. 
Kentucky  River,  118. 
Keyes,  C.  R.,  34,  39,  112,  113, 

Cited,  111. 
Kittatinny  limestone,  76,  99. 

Fossils  from,  100.  34B. 
Kuckers  shales,  Fossils  from,  228. 


Lake    Champlain    area,    Fossils    of,    261, 

271,   310. 

L/apparent,  A.  de,  27. 
Lapworth,  Charles,  26,  27. 
Le  Gore,  111. 

Exposures  at,  115,  116. 
Lebanon  limestone,  118. 

Fossils  from,  229. 
Lehigh  Valley,  76,  120. 
Leitersburg,  82,  86. 

Lenoir  limestone,  118,  120,  126,  129,  261. 
Lesley,  J.  P.,  38,  40. 
Licking  Creek,  Pa.,  Section  of,  95. 


Little  Antietam  Creek,  66. 

Fossils  from,  234. 
Little  Falls  dolomite,  74. 
Llandovery  Group,  25. 
Lorraine,  N.  T.,  Fossils  from,  289. 
Loudon  formation,  48,  53,  54,  88. 

Conglomerates  of,  54. 

Thickness  of,  53. 
Loudon  slate,  54. 
Lower  Cincinnatian  shales,  167. 
Lower  Martinsburg  shale,  Fauna  of,  165. 
Lower  Maysville,  156,  157,  160,  161,  170, 

171. 

Lower  Medina,  171. 
Lower  Ozarkian,  83. 
Lower  Stones  River,  122. 

Fauna  of,  122. 

Thickness  of,  123. 
Lower  Trenton,   156. 

Fossils  from,  216. 
Lowville  age,  133. 
Lowville  limestone,   136,   151,   153. 
Ludlow.  26. 


M 

McConnellsburg,   160,   169,  172. 

Fossils  from,  221,  222,  225,  237,  242, 
251,  253,  265,  266,  272,  275,  276, 
282,  283,  284,  285,  287,  288,  289, 
290,  296,  311,  325,  334,  356,  372. 
Macfarlane,  J.  R.,  39. 
Maclure,  William,  35. 
Maclurea  limestone,  298. 
McMillan  formation,  161,  171. 
McMullen,  H.  A.,  5. 
Mapleville,  59. 
Maquoketa  shale,  320. 
Mnrcou,  Jules,  36. 
Marion,  Fossils  from,  202,  273. 

Section  at,  145,  146. 
Martinsburg,  W.  Va.,  122,  123,  133,  140, 

154. 

Martinsburg  shale,  49,  110,  129,  130,  142, 
143,  145.  146,  147,  148,  149,  150,  151, 
154,  157,  160,  161,  171. 
Areal  distribution  of,  161. 
Faunas  of,  163,  164. 
Lithologic  character  or,  157. 
Section  of,  157. 
Topographic  features  of,    161. 
Martinsburg  shale  belt,   77,  89,   94,   103. 
106,  191. 

Section    east   of,    144. 
Massanutten  Mountain,  154. 
Massanutten   syncline,  80,   81,   130,   154, 

156.  158,  160,  161,  165. 
Mathews,  E.  B.,  7,  9,  43. 


GENERAL  INDEX 


413 


Mnugansville,   128. 

Fossils  from,  238,  247. 
Mayhill   sandstone.    26. 
Maysville  age.   163. 

Maysville  division,   Fossils  of.   168,   170. 
Meek.  F.  B.,  cited,  236,  253,  275,  279. 
Mercersburg,   Pa.,   147. 

Fossils  of,    166. 

Section  2%  mi.  S.  B.  of,  151. 
Mercersburg  Quadrangle,  Fauna  of,  165. 
Middle  Chazy  limestone,  126. 
Middle  Chazyan,  Fossils  from,  328. 
Middle  Chazyan  faunas,  127. 
Middle  Cincinnatian  division,  168. 
Middle  Ozarkian  formation,  83. 
Middle  Stones  River,  124,  126. 

Fauna  of,  124. 

Middleville,  Fossils  from,  234,  330. 
Miller,  S.  A.,  cited,  245,  251,  324. 
Millers  Chapel,   86. 
Mingan  Islands,  Fossils  from,  196. 
Minnesota,   Fossils  from,   197,   216,   217, 
218,  224,  228,  230,  232,  249,  258,  268, 
315,  333,  349. 
Mississippi  River,  136. 
Mississippi  Valley,  139. 

Fossils  from,  203,  219,  241,  248,  263, 

273,  278. 

Mitchlll,  S.  L..  35. 

Mohawk  Valley,  Fossils  from,   303,   304. 
Mohawkian  age,  117. 
Mohawkian  rooks,  Fossils  from,  198. 
Mohawkian  series,  156. 
Montalto  Mountain,  Pa.,  57. 
Montalta  quartzite  member,  57. 

Thickness  of,  57. 
Moore,  E.'S.,  44. 
Mosheim  limestone,  118. 
Murchison,  Sir  R.  I.,  cited,  25,  26. 
Murfreesboro  limestone,  118,   120. 

N 

Narraway,  J.  E.,  351. 

Cited,  348. 
Nason,   F.  S.,  87. 
National  Highway,  97,  330,  363. 

Exposure  along,  105. 
New  Brunswick,  Fossils  from,  246. 
New  Jersey,  76.  99,  120. 

Fossils  from,  100,  195,  197,  232,  234, 
246,  268,  270,  306,  307,  346,  351, 
353. 

New  Mexico,  Fossils  from,  238. 
New  York.  90.  99,  118,  120,  126,  171. 

Fossils  from,  100,  191,  202,  231,  232, 
234.  238,  239,  248,  254,  257,  270, 
273,  277,  278,  281,  282,  284,  285, 
291.  306.  307,  321,  323,  325,  326, 
327,  328,  329,  333,  346,  354,  359. 


Newfoundland,    Fossils    from,    246,    294, 

297,  299,  341. 
Nicholson,  Dr.,  cited,  193. 
Nidulites  bed,    132,    133,    140.    144,    145, 

146,  147,  148,  149,  150,  151,  152,  153, 

154. 

Fauna  of,  141. 
Nittanny  dolomite,  101. 
Xittanny  Valley,  101. 
Norfolk  and  Western  Railroad,  85,   190. 
Normanskill,  Fossils  from,  206. 
North  Mountain,  73,  110,  133,  147,  156, 

163. 


Observatory  Hill,  60. 
Ohio.  67. 

Fossils  from,  233,  281. 
Ohio  Valley,  160,  161. 

Fossils  from,  202,  203,  211,  214,  215, 
221,  222,  231,  237,  248,  253,  255, 
260,  272,  273,  278,  282,  283,  284, 
285,  312,  315. 
Oneida  conglomerate,  170. 
Ontario,  90. 

Fossils  from,  234,  333. 
Oolites,  78,  86,  93. 
Orbigny,  Alcide  d',  cited,  26. 
Ordovician,   23,    26. 

Columnar  sections  of,  48,  49. 

Correlation  table  of,  50. 

Geology  of,   24. 

History  of,  25. 

Paleogeography  of,  45. 

Paleontologic  characteristics  of,   50. 

Physiography  of,  23. 

Stratigraphic  characteristics  of,  50. 
Orthorhynchula  bed,  160,  168,  272. 

Fossils  of,  170. 
Oswegan  series,  170. 
Oswego  sandstone,  161,  170,  171,  282. 
Ozarkian,   88,  89. 
Ozarkian  fossils,  89. 
Ozarkian  limestone,  Fossils  from,  190. 
Ozarkian   system,   30,   31. 


Paleogeography,  Cambrian,  45. 

Ordovician,  45. 

Paleozoic  rocks,  Classification  of,  30. 
Parr's  Ridge,  24. 
Peabody,  Charles,  43. 
"  Peach  lands,"  67. 
Pen  Mar,  Pa.,  57,  58. 


414 


GENERAL  INDEX 


Pennsylvania,  24,  60,  62,  66,  67,  68,  70, 
73,  83,  96,  99,  101,  118,  120,  129,  132, 
133,  142,  143,  144,  153,  156,  158,  160, 
163,  167,  168,  171,  172. 

Fossils  from,  190,  194,  195,  204,  210, 
211,  217,  219,  224,  225,  230,  231, 
234,  246,  249,  254,  257,  260,  264, 
267,  270,  272,  274,  277,  282,  290, 
292,  298,  319,  337,  344,  345,  349, 
370,  371. 
Piedmont  Plateau,  23,  24,  111. 

Division  of,  24. 
Pierce  limestone,  118. 
Pinesburg   Station,    122,    126,    128,    132, 
139,  144,  151,  156,  158,  161,  167. 

Fossils  from,  194,  195,  201,  208, 
216,  218,  219,  229,  230,  240,  241, 
248,  249,  263,  264,  268,  298,  337, 
365. 

Pinesburg- Wilson  area,  132. 
Platteville  limestone,  365. 
Point  Levis,  Fossils  from,  246. 
Pondsville,   59. 
Potomac  River,  32,  53,  54,  57,  82,   147, 

132,  161. 

Potsdam  sandstone,  27,  74. 
Powell  Mountain,  163. 
Preface,  19. 
Prosser,  C.  S,  34,  42. 
Prosser  limestone,  Fossils  from,  216. 
Proterozoic  limestones,  84. 
Pulaski  shale,  171,  275,  287,  288. 
Fossils  from,  325. 


Quebec,  Fossils  from,  246. 
Queenston.'-Richmond  formations,  171. 


Raver's  Run,  Fossils  from,  233. 

Raymond,  P.  E.,  127,  351. 

Cited,  238,  239,  240,  247,  261,  271, 
310,  338,  347,  348. 

Reading,  Pa.,  Fossils  from,  191. 

Red  Medina,  161,  168,  170,  171. 

Richmond  Group,  161,  171,  320. 
Fossils  from,  213,  214. 

Rickard  Mountain,  Fossils  from,  205,  211, 
222,  225,  237,  245,  255,  265,  275,  281, 
282,  292,  296,  297,  313,  315,  324,  342, 
356,  367,  370,  371,  372. 

Ridley  limestone,   118. 

Ringgold,  70,  73,  85. 

Roadside,  66. 

Rogers,  H.  D.,  37. 

Rogers,  W.  B.,  38. 

Rohrersville,  54,  59. 

Rome,  N.  Y.,  Fossils  from,  288. 

Rome  sandstone,  68. 


Rome  shale,  68. 
Ruedemann,  Rudolph,  331. 

Cited,  203,  204,   205,  206,  254,  256, 

328,  354,  368. 
Russell  shale,  68. 
Rysedorph  conglomerate,  254,   257,  354, 

369. 
Rysedorph  Hill,  Fossils  from.  369. 


Safford,  J.  M.,  117. 

St.  Thomas,  Pa.,  Fossils  from,  166,  244, 
251,  260,  267,  306,  315. 

Section  2%  mi.  south  of,  148. 
Salter,  J.  W.,  26. 
Sapp,  E.  H.,  7. 
Saratoga,  Trilobites  of,  76. 
Saratoga  Springs,  Fossils  from,  191. 
"  Saratogan,"  74. 
Saxton,  Pa.,  Fossils  from,  233. 
Scharf,  J.  T.,  38. 

Schuchert,   Charles,   28,   30,   42,   43,   45, 
170,  232. 

Cited,  198,  258,  263. 
Scofleld,  W.  H.,  cited,  292,  295,  315. 
Scotland,  Pa.,  76,  77. 

Fossils  from,  238,  352. 

Section  of  Conococheague  limestone 

•west  of,  77. 
Security,  82. 

Security  Cement  and  Lime  Company,  82. 
Sedgewick,  Adam,  cited,  25,  26,  27. 
Seely,  H.  M.,  87. 
Shady  limestone,  66. 
Sharpsburg,  58,  70,  73,  80. 

Fossils  from,   190. 
"  Shenandoah,"  61. 
Shenandoah  formation,  60. 
Shenandoah  limestone,  60,  66. 
Shenandoah  River,  57. 
Shenandoah  series,  117. 
Shenandoah  Valley,  24. 
Sherwood  limestone,  61,  66. 
Silurian,  Usage  of,  33. 
"  Silurian  System,"  25. 
Singewald,  J.  T.  Jr.,  7. 
Sinuites  bed,  141,  145,  150,  164. 

Fauna  of,  165. 
Sinuites  zone,  164. 
Smithsburg,  68,  70,  71. 

Fossils  from,  234,  339. 
South  Mountain,  24,  53,  54.  56,  58,   61. 

62,  64,  65,  69. 

Stonehenge  limestone,   78,    97,   99,    100, 
101,  106,  107. 

Fossils  of,  100. 

Stonehenge  member,  82,  93,  96,  106.  114. 
Stones  River,  Fossils  from,  202,  214,  227, 
229,  249,  295. 


GENERAL  INDEX 


415 


Stones  River  limestone,  49,  63,  92,  95, 
105,  108,  110,  117,  145,  146,  148,  149, 
150,  151,  152. 

Areal  distribution  of,  126. 
Fauna  of,  127,  128. 
General  sections  of,  117. 
Lithologic  character  of,   121. 
Paleontology  of,  121. 
Stose,  G.  W.,  20,  34,  43,  44,  57,  67,  72, 

76,  77,  87,  88,  94,  130,  230,  250. 
Stoufferstown,    Fossils    from,    291,    293, 

294,  302,  308,  327,   331. 
Strasburg,  Va.,  153,  163. 

Fossils  from,  197,  232,  235,  243,  257, 
267,  316,  317,  321,  355,  358,  373. 
Sugar  Loaf  Mountain,   56,  113. 
Swartz,  C.  K.,  7,  44. 
Sword  Mountain,  172. 


Taconic  system,  27. 
Taylor,  R.  C.,  36. 
Tennessee,  83,  117,  126,  127. 
Cedar  glades  of,  121. 
Fossils  from,  197,  206,  224,  227,  229, 
230,  238,  239,  248,  249,  272,  298, 
300,  344. 

Tetradium  cellulosum  bed,  133,  136,  144, 
145,  146,  147,  148,  149,  150,  151,  152, 
153,  154. 

Fauna   of,   137. 
Tomstown  formation,  73. 
Tomstown  limestone,  48,  58,  61,  64,  65, 
88,  89. 

Age  of,  66. 

Areal  distribution  of,  65. 
Correlation  of,  66. 
Economic  features  of,  64. 
Lithologic  characters  of,  62. 
Residual  products  of,  63. 
Topography  of,  61. 
Tomstown-Waynesboro  boundary,  69. 
Tomstown  Valley,  65. 
"  Transition  "  beds,  129. 
"  Transition  Series,"  25,  26. 
Trenton  age,  141,  156,  163,  165. 
Trenton  Falls,  Fossils  from,  235. 
Trenton  formation,  112  154,  157. 
Trenton    limestone,    27. 

Fossils  from,  197,  202,  203,  205,  226, 

232,  235,  269,  270,  315,  323,  326, 

327,  330,  333,  350,  351,  353,  354. 

Tribes  Hill  limestone,  Fossils  from,  192, 

329,  346,  362. 

Tribes  Hill  limestone  fauna,  99,  100. 
Trilobites,  76,  82,  89,  103,  113. 
Turner's  Gap,  53. 


Turritoma  zone,  93,  95,  96,  104. 

Fossils  of,  105. 
Tuscarora  Mountain,  168,  172. 

Fossils  from,  169,  222,  225,  242,  251, 
253,  266,  272,  275,  276,  282,  283, 
284,  285,  287,  288,  289,  296,  325, 
334,  356,  372. 

Section  along  west  slope  of,  173. 
Tuscarora  sandstone,  171,  172. 
Tyson,  P.  T.,  37. 


U 

Ulrich,  E.  O.,  20,  28,  29,  30,  31,  34,  42, 
43,  45,  47,  74,  87,  88,  93,  94,  99,  101, 
117,  122,  124,  130,  131,  132,  137,  139, 
142,  144,  146,  153,  163,  171,  172,  356. 
Cited,  213,  214,  216,  219,  224,  226, 
227,  228,  229,  278,  281,  286,  292, 
295,  296,  311,  334,  365,  368,  370. 
Upper  Chazyan,  154. 
Upper  Maysville,  157,  161,  171. 
Upper  Medina,  171. 
Upper  Ordovician  shales,  154,  161. 
Upper  Stones  River,  126,  140,  144. 
Utah,  Fossils  from,  238. 
Utica  shale,  27,  156. 
Fossils  from,  231. 


Valley  limestone,  60. 
Vanuxem,  Lardner,  304. 

Cited,  303. 
Vermont,  90. 

Fossils  from,  297,  302,  332. 
Virginia,   24,  61,   67,   83,   103,   111,   118, 
126,   130,  142,   163,   167. 

Fossils  from,  190,  191,  194,  217,  234, 
254,  257,  267,  272,  277,  292,  297, 
345. 


W 

Wagner's  Cross  Roads,  63,  70. 

Walcott,  C.  D.,  40,  41,  59,  66,  74,  84,  86, 

235,  319. 

Cited,  32,  238,  351. 
Walling,  H.  F.,  39. 
Washington   County,   Fossils  from,   204, 

234. 

Warrior  limestone,  83. 
Waucoban  fossils,  89. 
Wautaga  shale,  67,  68. 
Waynesboro,  57,  66,  67,  69,  74. 
Fossils  from,  230,  319,  339. 


416 


GENERAL  INDEX 


Waynesboro   formation,    48,    63,    65,    66, 
72,  73,  88,  89. 
Age  of,  71. 

Areal  distribution  of,  70. 
Correlation  of,  71. 
Economic  features  of,  71. 
Llthologic  character  of,  68. 
Name  and  synonymy  of,  67. 
Thickness  of,  68. 
Tomstown-Waynesboro  boundary  of, 

69. 

Waynesboro  sandstone,  61. 
Weller,  Stuart,  303. 

Cited,  195,  234,  236,  241,  243,  248, 
249,  268,  270,  273,  313,  314,  315, 
321,  335,  345,  353,  355,  358,  359, 
362. 

Wenlock,  26. 

West  Virginia,  123,  151,  153. 
Western  Maryland   Railway,   58,   62,   65, 
72,  80,  86,  99,  103,  139,  156,  161,  167. 
Weverton,  54. 
Weverton  quartzite,  53,  88. 
Weverton  sandstone,  48,  54,  61,  113. 
Composition  of,  55. 
Outcrops  in,  54. 
Thickness  of,  56. 


White    Medina     (Tuscarora)     sandstone, 

168,  171. 
Whitfleld,  R.  P.,  cited,  283,  285,  288,  367, 

370,  372. 

Williams,  G.  H.,  41. 
Williams,  R.  C.,  20. 

Williamsport,  110,  156,  158,  161,  167. 
Exposures  in,  103. 
Fossils  from,  203,  206,  231,  236,  246, 

267,  290,  292,  297,  299,  308,  316, 
336,   340,   342,  363,   372. 

Willis,  Bailey,  41,  44. 

Wilson,  Alice,  267. 

Wilson,  Md.,  132,  139,  141,  144,  151. 

Fossils  from,  194,  201,  208,  213,  214, 
217,  220,  240,  241,  248,  263,  264, 

268,  349,  365. 
Winchell,  N.  H.,  117,  232. 

Cited,  198,  258,  263. 
Wing,  Mr.,  87. 
"  Wing  Conglomerate,"  87. 
Wisconsin,  Fossils  from,  197,  330. 
Woods,  A.   F.,  5. 


York,  Pa.,  Fossils  of,  66,  88. 


PALEONTOLOGICAL  INDEX 


Figures  in  bold  face  indicate  principal   discussion. 


Acidaspis,  355. 

ulrichi,  117,  182,  355. 
Acrotretidse,    234. 
Actinoceratidse,  328. 
Actinostroma   trentonensis,    192. 
Alecto  inflata,  212. 
Algse,   82,   85,    189. 
Allonychia,  284. 

ovata,  170,  178,  284. 
Ambonychia  cincinnatiensis,  282. 

radiata,  282. 
Ambonychiidffl,  282. 
Amphilichas,   354. 

cf.  trentonensis,  136. 

trentonensis,   165,   166,   182,  354. 
Amphion  salteri,  359. 
Ampyx,  336. 

cf.   A.  normalis,   142. 

halli,  124,  337. 

(Lonchodomas)  halli,  128,  182,  337. 

(Lonchodomas)    normalis,    140,   180, 
336. 

normalis,  336. 
Amygdalocystidse,  141. 
Anastrophia  hemiplicata,  20U. 
Anodontopsis    (Modiolopsis)    unionoides, 
281. 

unionoides.  281. 
Anolotichia,   135. 
Anthozoa,  198. 
Aparchites,   137,   366. 

minutissimus,  169,  182,  366. 
Archeocyathus,  66. 
Arthroclema  spiniformis,  228. 
Arthropoda,    332. 
Arthropora,  224. 

bifurcata,    143,  176,  224. 

cleaveland,  169,  176,  225. 
Arthrostylidse,   227. 
Asaphellus,    345. 

gyracanthus,  100,  182,  345. 
Asaphidse,  342. 
Asaphus  canalis,   345. 

convexus,  347. 

gyracanthus,   347. 

(Isotelus)   megistos,  343. 

marginalis,  346. 

trentonensis,  354. 


Aspidobranchia,  289. 
Atremata,  23O. 
Atrypa  exigua,  273. 

heiniplicata,  269. 

modesta,  274. 

plena,  270. 

recurvirostris,  272. 
Avicula  demissa,  284. 
Aviculidae,  284. 

B 

Bathyuridae,  34O. 
Bathyurus,   136,  347. 

caudatus,  340. 

conicus,  340. 

levis,  347. 
Bastostoma,  22O. 

cf.  B.  magnoporum,  135. 

irrasa,  218. 

jamesi,  169,  174,  22O. 
Batostomellidse,  221. 
Beatricea,  137,  148,  150. 
Bellerophon  bilobatus,  313. 

cancellatus,  313. 

sulcatinus,  309. 
Berenicea,  214. 

veslculosa,  169,  174,  214. 
Beyrlchia  chambers!,   369. 
BeyrichiidfE,  367. 
Billingsellidsa,  237. 
Bolboporites,  141. 
Brachiopocla.  23O. 
Branchiopoda,  362. 
Bryozoa,  212,  220. 
Bucania,  3O9. 

champlainensis,  309. 

sulcatina,  124,  128,  180,  3O9. 
BucaniidfB,   3O9. 
Bumastus,  351. 

milleri,  351. 

trentonensis,  164,  166,  182,  351. 
Byssonychia,   282. 

praecursa,  170.  178,  283. 

radiata,  178,  282,  283. 

vera,  169,  178,  282. 
Bythocypris,    371. 

cylindrica,  169,  182,  371. 
Bythopora,  221. 

arctipora,    169,   174,   221. 


418 


PALEONTOLOGICAL  INDEX 


Calcareous  Algae,  82,  193. 
Callopora  onealll  sigillaroides,  222. 

sigillarioides,  222. 
Calymene,  356. 

becki,  342. 

callicephala,  356. 

callicephala  granulosa,  356. 

granulosa,  169,  182,  356. 

senaria,  164,  166,  182,  357. 
Calymenidse,  356. 
Camarocladla,   196. 

rugosa,  174,  196,  137. 
Camarotoechia,  27O. 

plena,  135,  136,  178,  270. 
Camerata,  2O9. 
Camerella  minor,  233. 
Cameroceras,  117,  180,  321. 
Carabocrinus,  135,  142,  174,  2O9. 
Caritodens  demissa,  284. 
Caryocarls,  372. 

slllcula,  167,  182.  372. 
Caryocystites,   133,   135,   174,  2O8,   209. 
Catazyga  erratica,  275. 
Cephalopoda,  321. 
Ceratopea,  93,  95,  103,  299. 

keithi,  104,  178,  299. 
Ceratopsis,  369. 

chambers!,  169,  182,  369. 
Ceraurus,  358. 

pleurexanthemus,  137,  142,  182,  358. 
Cerionites,  194. 
Chaetetes,  201. 

Jamesi,  220. 

sigillarioides,  222. 
Chaetetidse,  199. 
Chasmatopora,  226. 

reticulata,  136,  176,  226. 

sublaxa,  136,  176,  227. 
Chelruridae,  358. 
Christiania,  256,  257. 

lamellosa,  165,  166,  176,  257. 

trentonensis,    142,    143,    152,    176, 

256. 

Cirripedia,  371. 
Clathrospira,  137. 
Cleiocrlnus,  137,  149. 
Clidophorus,  28O,  320. 

planulatus,  169,  178,  28O. 
Cliftonia,  267. 
Climacograptus,  2O2. 

blcornis,  169,  174,  203,  2O4. 

putillus,  167,  174,  2O2. 

splnifer,  167,  174,  2O3. 

typicalis,  203. 
Clitambonitidse,  268. 
Ccelenterata,  198. 
Coleolus,  32O. 

iowensis,    164,    165,    166,    180,    32O. 


Columnaria,   198. 

alveolata,  198. 

halli,  135,  174,  198. 
Conotreta,  234. 

rusti,  164,  166,  176,  234. 
Constellariidae,  217. 
Conularia,  32O. 

trentonensis,  164,  166,  180,  32O. 
Conulariida,  319. 
Conulariidae.  32O. 
Cornulites,  276. 

flexuosus,  169,  178,  276. 
Corynexochidae,   338. 
Corynoides,  157,  2O6. 

calicularis,  165,  167,  174,  2O6. 
Corynotrypa.  212. 

delicatula,  142,  174,  213. 

inflata.  142,  174,  212. 
Craniidse,  236. 
Crinoidea,   2O9. 
Crustacea,  332. 
Cryptolithus,  143,  333. 

bellulus,  169,  180,  333. 

recurvus,  169,  180,  33*4. 

tesselatus,   164,   165,  167,   180,  335. 
Cryptostomata,  223. 

Cryptozoon,  76,  82,  83,   85,  86,  89,  101, 
102,  106.  107,  189,  190,  191. 

proliferum,  78,  82,  85,  89,  174,  189, 
190. 

steeli,  93,  94,  95,  102,  174,  191. 

undulatum,  78,  82,  89,  174,  19O. 
Ctenodonta,  143,  277,  279. 

cf.  C.  gibberula,  136. 

filistriata,  169,  178,  279. 

glbberuln,  137,  ^78,  277. 

levatn,  279. 

obliqua,  169,  178,  278,  320. 
Ctenodontidae,  277. 
Cyathocrinidae,  2O9. 
Cyathophyllldae,   198. 
Cyathophyllum  profundum,  199. 
Cycloceratidae,  325. 
Cyclonema,  316,  317. 
Cyclora,  316. 

hoffmanni,  164,  165,   166,  180,  317. 

minuta,  164,  165,  166,  167,  180,  279, 
316,  317,  320. 

parvula,  164,  165,  166,  180,  316. 
Cyclostomata,  212. 
Cyclostomiceras,  331. 

cassinense,  100,  180,  331. 
Cyphaspis,  353. 

matutina,  164,   165,   166,   182,  353. 
Cypricardites  nasuta,  289. 
Cypridae,  371. 
Cyrtoceras,  329. 

beekmanense,  100,  180,  33O. 

camurum,  144,  180,  33O. 


PALEONTOLOGICAL 


419 


gracile,  100,  180,  329. 

klrbyi,  328. 
Cyrtocerina,  331. 

mercurius,  105,  331. 
Cyrtochoanites,  328. 
Cyrtodonta,  122,  136,  137. 
Cyrtodontidae,    281. 
Cyrtolites  (Microceras)  Inornatus,  312. 

trentonensis,  306. 
Cyrtolitidae,  311. 
Cyrolitlna,  311. 

nltidula,  165,  180,  311. 
Cystoidea,  2O7. 
Cytherina  fabulites.  364. 


Dalmanella,  94,  242. 

edsoni,  165,  166,  176,  243. 

electra,  104,  105,  176,  245. 

multisecta,  169,  176,  244. 

(Orthis)  wemplei,  246. 

subaequata,  249. 

testudinaria,  140,  142,  164,  165,  166, 
176,  242. 

testudinaria  var.  multisecta,  244. 

wemplei,  99,  100,  176,  246. 
Dendrocrinidse,  211. 
Dianulites,  217. 

petropolitana,  217. 

petropolitanus,  140,  174,  217. 
Diastoporidae,  212. 
Dikelocephalidse,  351. 
Dinorthis,  247. 

cf.  D.   subquadrata,  143. 

pectinella,  140,  176,  248. 

(Plzesiomys)    platys,   128,   176,  247. 

platys,  124,  247. 
Diplograptidse,  2O2. 
Diplograptus,  2O5. 

foliaceus  mut  vespertinus,  205. 

pristis,  205. 

vespertinus,  169,  174,  2O5. 
Diplotrypa,  141,  219. 

appalachia,  141,  142,  149,  174,  219. 
Dlscinidae,   234. 

Dolichometopus,  74,  89,  182,  338. 
Drepanella,  367. 

macra,  137,  182,  367. 


Eccyliomphalus,   305. 

multiseptarius,  100,  180,  3O5. 

trentonensis,  165,  166,  180,  3O6. 

triangulus,   oo2. 
Eccyliopterus,  94,  3O1. 

disjunctus,  105,  180,  3O1. 

triangulus,    102,    180,  3O2. 
Echinodermata,  207. 


Echinosphaerites,  139,  144,  152,  2O7. 

aurantium  americanum,  139,  143. 

174,  207. 

Echinus  aurantium,  207. 
Endoceratidae,  321. 
Eoharpes,  332. 

ottawaensis,  164,  166,  180,  332. 
Eoorthis,  237. 

cf.  desmopleura,  82,  89,  176. 

desmopleura,  237. 

remnicha,  237. 

wichitaensis,  237. 
Escharopora,  223. ' 

cf.  ramosa,  140. 

confluens,  136,  174,  223. 
Eucrustacea,    362. 
Eunema  cf.  E.  salterl,  137. 
Euomphalidae,  297. 


Favosites,  201. 
Fucoldes  linearis,  276. 


Gastropoda,  289. 
Girvanella,   122. 
Gomphoceras  cassinense,  331. 
Gonioceras,  328. 

chazlense,  136,  180,  328. 
Goniurus,  34O. 

caudatus,  104,  182,  34O. 
Graptodictya,  136. 
Graptolite  germs,  206. 
Graptolithus  bicornls,  204. 

putillus,   202. 
Graptolitoidea,  2O2. 
Graptoloidea,  2O2. 

H 

Hallopora,  222. 

onealli  sigillaroides,  169,  174,  222, 
Halloporidse,  222. 
Harpedidse,  332. 
Harpina  ottawaensis,  332.  • 
Hebertella,  238. 

bellarugosa,  136,  140,  176,  239. 

borealis,  124,  128,  136,  176,  238. 

vulgarls,  124,  128,  135,  136,  176. 

239. 
Helicotoma,  122,  3OO. 

planulata,  300. 

planulatoides,  137,  150,  178,  3OO. 
301. 

verticalis,  137,  178,  3O1. 
Helopora,  227. 

divaricata,  136,  176,  227. 

spinlformis,  139,  176,  228. 


420 


PALEONTOLOGICAL  INDEX 


Hemigyraspis,  346. 

collieana,  100,  182,  346. 
Hemiphragma,  218. 

cf.  H.  irrasum,  143. 

irrasum,  136,  140,  174,  218. 
Heterocrinidffi,  21O. 
Heterocrinus,  21O. 

heterodactylus,  169,  174,  21O. 
Hindia,  197. 

parva,  165,  166,  174,  197. 

sphseroidalis,  197. 
Hindlidse,  197. 
Hippothoa,  212. 

delicatula,  213. 
Holochoanltes,  321. 
Holopea,  316. 

nana,  316. 
Hormotoma,  291,  31  <. 

artemesia,   104,   178,  291. 

gracilens,  105,  178,  293. 

gracills,  169,  178,  292. 
Hudsonaster,  211. 

clarki,  loo,  174,  211. 

matutlnus,  211. 
Hudsonasteridae,  211. 
Hyolithidse,   318. 
Hyolithes,  318. 

communis,  59,  89,  180,  318. 
Hypoparia,  332. 
Hystricurus,  34O. 

conicus,  102,  182,  34O. 


Illaenidae,  349. 

Illaenurus  columbiana,  347. 

Illnenus,    142,    143,    349. 

americanus,  165,  166,  182,  349. 
Inadunata,   2O9. 
Intricaria  reticulata,  226. 
Ischadites,   139,   194. 
Ischyrodonta,  281. 

curta,  281. 

unionoides,  170,  178,  281. 
Isochilina,  363. 

amiana,  363. 

cf.  I.  gracills,  136,  137. 

cf.  I.  Ottawa,  137. 

gregarla,  104,  182,  363. 

Ottawa  var.  Intermedia,  363. 

seelyi,  105,  182,  363. 
Isotelus,   117,   137,   182,   342,  345,   348. 

canalis,   345. 

gigas,  143,  182,  342,  343,  344. 

maxlmus,  343. 

megistos,   170,   182,  343. 

stegops,   169,  182,  342. 


'Ledidae,  28O. 
Leperditella,  366. 

tumlda,  137,  182,  366. 
Leperdltla,  150,   151,  364. 

bivertex,  370. 

cf.  L.  fabulites,  136,  140,  142. 

fabulites,    122,    124,    127,    128,    129, 
137,  152,  182,  364. 

(Isochilina)    cylindrica,  371. 

(Isochilina)   minutissima,  366. 

tumida,  366. 
Leperditiidae,  363. 
Lepidocoleidse,   371. 
Lepidocoleus,  143,  371. 

jamesi,  167,  169.  182.  371. 
Leptaena,  142,  149,  257,  260. 

alternata,  265. 

cf.  L.  charlottse,  143. 

charlottae,  136.  176,  250,  257. 

gibbosa,    169,    176,    259. 

rhomboidalis,  258. 

sericea  var.  rugosa,  255. 

tenuistriata,  165,  166,  176,  26O. 
Leptobolus,  23O. 

insignis,   167.   176.  231. 

ovalis,   164,  165,  166,  176,  23O. 
Lichadidae,   354. 
Lichenarla,  220. 

Llcrophyciis  cf.   L.   ottawaense,    139. 
Lingula,  151,  232. 

elderl,  233. 

(Glossina)   riclnlfonnis.  232. 

nicklesl,  170,  176,  232. 

rectilateralis,  233. 

rlcinlformis,  164,  165,  166,  176,  230, 

232. 

Lingulella,  71.  89,  176,  23O. 
Lingulidae,  232. 
Liospira,  93,  104,  296. 

cf.  perangulata,  122. 

micula,  169,  170,  178,  296. 
Lituites  internistriatus,   326. 
Lockeia,    139. 
Lonchodomas  halli.  337. 
Lophospira,  294. 

blcincta.  124.  128.  178.  294. 

cf.  L.  procera,  137. 

(Ruedemannia)  Hrata,  169,  178.  295. 

(Seelya)   lirata,  295. 

trochonemoides,  122. 
Lyrodesma,  286. 

conradi,   169.   178,  286. 
Lyrodesmidae.  286. 


K 


Klcedenia,  137. 


Maclurea,  299. 
magna,  297. 
oceana,  299. 
sordida,  298. 


M 


PALEONTOLOGICAL  INDEX 


421 


Maclurites,  94,  98,  103,  104,  297. 

afflnis,  102,  178,  297. 

magna,  297. 

magnus,  118,  120,  124,  128,  178,  297. 

oceanus,  105,  178,  299. 

sordida,    93. 

sordidus,  104.  178,  298. 
Macronotella,  368. 

ulrichi,  137,  182,  368. 
Malacostraca,  372. 
Matheria,  122. 
Merocrinus,  169,  174,  211. 

curtus,  211. 
Mesonacidse,  339. 
Mesotrypa,   142. 
Microceras,  312. 

inornatum,  164,  165,  166,  180,  312. 
Modiolodon,  288. 

truncatus,   170,   178,  288. 
Modiolopsidse,  28tf. 
Modiolopsis,  286. 

modiolaris,    170,    178,  286. 

nasutus,  289. 

truncatus,   288. 
Mollusca.  277. 
Molluscoidea,  212. 

Monotrypa   (Chsetetes)    cumulata,  217. 
Monticulipora  (Heterotrypa)  jamesi,  220. 

wetherbyi,  214. 
Monticuliporidse,  214. 
Murchisonia  acrea.  293. 

alexandra,   308. 

artemesia,  291. 

bicincta,  294. 

gracilens,  293. 

gracilis,  292. 

N 

Nautiloidea,  321. 
Neotremata,  233. 
Nicholsonella  cf.  N.  laminata,  135. 
Nidulites,  141,  144,  193. 

pyriformis,  141,   174,  193,  220. 
Notostraca,  362. 
Xucula  obliqua,  278. 
Nuculites,  362. 

plnnnlata,    280. 


Obolella,  232,  233. 

minor,  59,  89,  176,  233. 
Obolellidse,  233. 
Obolidae,  230. 
Odontopleuridae,  355. 
Olenellus,  66,  71,  339. 

thompsoni,  59,  89,  182,  339. 
Olenidse,  341. 
Omospira,  308. 

alexandra,  137,  180,  3O8. 


Onchometopus,  348. 
obtusus,   348, 
simplex,  142,  182,  348. 

sus;r,   348. 

Oncoceras,  122. 
Oncoceratldae,  331. 
Ooceras,  328. 

kirbyi,  100,  180,  328. 
•  Ophileta,  94,  95,  98,  3O2. 

compacta,  102,  180,  3O4. 

complanata,  99,  100,  180,  3O2,  303, 
304,  305. 

discus,   304. 

disjuncta,  301. 

levata,  100,  180,  3O4. 
Opisthobranchia,   318. 
Opisthoparla,  338. 
Orbicula  fllosa,  235. 

lamellosa,  234. 
Orbiculoidea,  234. 

lamellosa,   143,    176,  234. 
Orbignyella,  214. 

•wetherbyi,  137,  174,  214. 
Orocystites,  139. 
Orthacea,  237. 
Orthidse,  238. 
Orthls,  240. 

bellarugosa,  239. 

borealis,  238. 

(Dalmanella)    subaequata,  249. 

desmopleura,  237. 

(Dinorthis)   pectinella,  248. 

electra,  245. 

emacerata  var.  multisecta,  244. 

erratica,  275. 

(Hebertella)   bellarugosa,  239. 

linneyi,  271. 

merope,  268. 

multisecta,  244. 

pectinella,  248. 

platys,  247. 

(Plectorthis)  desmopleura,  237. 

plicatella,  241. 

subaequata,  249. 

testudinaria,  242. 

tricenaria,  142,  143,  176,  24O. 
Orthoceras,  122,  137,  322,  323. 

arcuoliratum,   144,  180,  323. 

Junceum,    164,    165,    166,    180,   323. 

lamellosum,  170,  180,  324. 

primigenium,  100,  180,  322. 

transversum,   169,   180,  324. 
Orthoceratidse,    322. 
Orthochoanites,  322. 
Orthodesma,  289. 

nasutum,  170,  178,  289.. 
Orthorhynchula,  271. 

linneyi,  157,  160,  168,  170,  178,  271. 
Ostracoda,   363. 


422 


PALEONTOLOGICAL  INDEX 


Oxoplecia,  267. 

calhouni,  267. 


Pachydictya  cf.  P.  robusta,  136. 
Palaeophycus,  141,  192. 

tubulare,  100,  174,  192. 
Parastrophia,  269. 

hemiplicata,  143,  178,  269. 
Paterula,  231. 
Pelecypoda,  277. 
Pentameracea,  267. 
Phacoplda3,  36O. 
Phacops  callicephalus,  360. 
Pholidops,  236. 

cincinnatiensis,  169,  176,  236. 
Phyllocarida,  372. 
Phylloporina  reticulata,  226. 

sublaxa,  227. 
Phylloporinlda?,  226. 
Phytopsis  cellulosum,  202. 
Pianodema,  249. 

cf.  P.  subsequata,  142,  149. 

subsequata,  140,  176,  249. 
Plsesiomys  platys,  247. 
Platymetopus  trentonensis,  354. 
Platystrophia,  266. 

Plectambonites,  136,  140,  142,  143,  253, 
255,  257. 

cf.  P.  plsum,  142. 

cf.  P.  sericeus,  149. 

plsum,  140,  143,   176,  253. 

rugosus,  169,  176,  255. 
Plectorthis,  241. 

aff.  P.  Whitfleldi,  142. 

plicatella,   169,  170,  176,  241,  242. 
Pleurocystidae,  141. 
Pleurotomaria,  289,  29O,  291. 

canadensis,  104,  178,  289. 

florldensis,  178,  291. 

gregarla,  105,  178,  29O. 

hunterensis,  302,  303. 

laurentina,   308. 

mlcula,  296. 
Pleurotomariidse,  289. 
Pliomerops,  359. 

salteri,  104,  182,  359. 
Plumulites  jamesi,  371. 
Polygyrata,  303. 
Porambonitidse,  /69. 
Porifera,  195. 
Porocrinus,  142. 
Prasopora,  215. 

contigua,  142,  174,  216. 

insularis,  140,  174,  215. 
Primitia,  137. 

gregaria,  363. 

seelyi,  363. 
Prion  odesmacea,  277. 


Proetidse,  352. 
Proetus,  352. 

latimarginatus,  164,   166,  182,  352. 
Proparia,  356. 
Protorhyncha,  137. 
Protowarthia  cancellata,  313. 

granistriata,  314. 
Protozyga  exigua,  273. 
Protremata,  237. 
Pterinea,  284. 

(Caritodens)  demissa,  170,  178,  284. 

demissa,  284. 

modiolaris,  286. 
Pteropoda,  318. 
Pterygometopus,  36O. 

callicephalus,  137,  182,  36O. 

cf.  P.  callicephalus,  142. 

cf.  P.  schmidti,  140. 
Ptilodlctya  arctipora,  221. 

cleavelandi,  225. 
Ptilodictyonidse,  223. 


Rafinesquina,  140,  261. 

alternate,  170,  176,  258,  264,  265. 

cf.  R.  incrassata,  142. 

champlainensis,  136,  176,  261. 

minnesotensis,   140,   176,   261,   264. 

minnesotensis    inqunssa,    140,    176, 
264. 

squamula,  169,  170,  176,  264. 
Raphanocrinus,  139. 
Raphlophoridae,  336. 
Raphistoma,  3O7. 

columbianum,  100,  180,  3O7. 

obtusum,   100,  180,  3O7. 
Raphistomidffi,  3O7. 
Raphlstomina,  3O8. 

laurentina,   104,  180,  308. 
Receptaculites,  194. 

occidentalis,  139,  174,  194. 
Reteocrinidae,  2O9. 
Reteocrinus,  117,  174,  2O9. 
Rhabdaria,  195. 

fragilis,  102,  174,  195. 
Rhinidictya,  229. 

cf.  R.  neglecta,  143. 

fidelis,   136. 

neglecta,  140,  176,  229. 
Rhinidictyonidae,  229. 
Rhipidomellidse,  247. 
Rhynchonellacea,  27O. 
Rhynchonellidse,  27O. 
Ribeiria,  362. 

nuculitiformis,  100,  182,  362. 
Ruedemannia  lirata,  295. 


PALEONTOLOGICAL  INDEX 


423 


s 

Salterella,  66,  89,  180,  319. 
Saukia,  351. 

fallax,  351. 

pepinensis,  351. 

stosei,  82,  89,  182,  351. 
Scenidlum,  268. 

anthonense,  142,  178,  268. 

anthonensis,  268. 

cf.  S.  anthonense,  143. 

halli,  268. 

merope,  165,  16S,  178,  268. 
Schizocrania,    235. 

fllosa,  167,  176,  235. 
Scolithus,    57,    276. 

linearis,   58,   89,   17S,  276. 
Slnultes,  157,  158,  313. 

cancellatus,  163,  164,  165,  166,  169, 
180,  313,  314. 

granistriatus,    164,    165,    166,    169, 

180,  314. 
Sinuitidse,  313. 
Solenopleuridse,  34O. 
Solenopora,  192. 

compacta,   122,   135,   148,  174,  192, 
193. 

spongioides,   192. 
Spongiae,   193. 
Spyroceras,  325. 

bilineatum,  165,   166,  180,  325. 
Stelleroidea,  211. 
Stenopora  fibrosa,  195. 
Stictopora   paupera,   229. 
Stictoporella,  142. 
Stomatopora  proutana,  213. 

tenuissima,  213. 
Streptelasma,  199. 

profundum,  137,  174,  199. 
Streptorhynchus  hallie,  251. 
Stromatotrypa,  142. 
Strophomena,  143,  25O. 

alternate,  265. 

cf.  S.  emaciata,  137. 

cf.  S.  filitexta,  140,  142. 

deltoidea,  261. 

gibbosa,  259. 

hallie,  169,  176,  251,  257. 

(Hemipronites)   sinuata,  252. 

inquassa,  264. 

sculpturata,  164,  165,  166,  176,  25O. 

sinuata,  169,  176,  250,  252. 

squamula,   264. 

stosei,  117,  176,  25O. 
Strophomenacea,  25O. 
Strophostylus,  315,  316. 

textilis,  165,  166,  180,  315. 
Symphysurus,  347. 

convexus,  100,  182,  347. 


Syntrophia,  267. 

lateralis,  93,  102,   104,  178,  267. 


Tabulata,  199. 
Tellinomya  obllqua,  278. 

ventricosa,  277. 
Telotremata,  27O. 
Tentaculites  flexuosa,  276. 
Tetrabranchiata,  321. 
Tetracoralla,  198. 
Tetractinelllda,   197. 
Tetradium,  121,  199,  200. 

cellulosum,  133,  136,  137,   148,  149, 
150,  174,  202. 

columnare,  135,  174,  2O1. 

peachli  var.  canadense,  192. 

simplex,  102,  174,  199. 

syringoporoides,  122,  124,  126,  127, 

128,  129,  152,  174,  2OO. 
Tetranota,  31O. 

bldorsata,  310,  311. 

obsoleta,    169,    180,    31O. 
Thallophyta,  189. 
Torellellidae,  319. 
Trematidae,  235. 

Trematopora  cf.  primigenia,  143. 
Trematoporidae,  218. 
Trepostomata,  214. 
Tretaspis,  143. 
Trlarthrus,  341,  342. 

becki,  164,  165,   166,  167,  169,   182, 
341,  342. 

flscheri,  164,  166,  182,  341. 
Trllobita,  332. 
Trinucleldae,  333. 
Trlnucleus  concentricus,  335,  336. 
Triplecia,  266,  267. 

cf.  T.  nucleus,  143. 

(Cllftonia)  simulatrix,  140,  142,  143, 
165,   166,   178,  266. 

lateralis,  267. 
Trocholites,  326. 

ammonius,  164,  166,  180,  327. 

internistrlatus,  105,  180,  326. 
Trocholitidae,  326. 
Trochonematidaa,  315. 
Tubicola,  276. 
Turbo  parvulus,  316. 
Turritella,  293. 
Turritoma,  104,  293. 

acrea,  104,  105,  178,  293. 


U 

Ulrlchia,  37O. 

bivertex,  169,  182,  37O. 


42-i  PALEONTOLOGICAL  INDEX 

v  z 

Verities,   276.  Zaphrentidse,  199. 

Zygospira,  272. 

erratica,  170,  178,  275. 

W  exigua,  143,  178,  273. 

Wingiu.  87.  modesta,  169,  170,  178,  274,  275. 

Worm  burrows,  27(5.  rocurvirostris,  136.  137,  178,  272. 


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